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PubMed2026

The RrWRKY75-mediated activation of ascorbate synthesis in Rosa roxburghii Tratt contributes to salt stress tolerance.

L-Ascorbic acid (AsA) is a key antioxidant that alleviates oxidative stress in plants. Previous yeast one-hybrid (Y1H) screening identified RrWRKY75 as a transcription factor capable of binding to the promoter of RrGGP2 (GDP-L-galactose pyrophosphatase 2), a key structural gene responsible for massive AsA accumulation in Rosa roxburghii fruit. The function of RrWRKY75 in plant stress responses remains unclear. Here, RrWRKY75 is verified to specifically bind to the RrGGP2 promoter and activate its transcription. This positive regulatory effect on RrGGP2 transcript levels and AsA accumulation is further confirmed through overexpression or silencing of RrWRKY75 in R. roxburghii fruit or callus. Among various abiotic stress conditions, RrWRKY75 expression is significantly induced by salt stress. Upon its overexpression in callus or Arabidopsis thaliana, elevated AsA levels and antioxidant capacity are observed, thereby enhancing salt tolerance. Interestingly, RrWRKY75 also binds to the promoter of RrUNE12, a salt-responsive factor in R. roxburghii, and activates its expression. Moreover, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays confirm the physical interaction between RrWRKY75 and RrUNE12, which jointly upregulates RrGGP2 expression and AsA production. Collectively, RrWRKY75 boosts AsA biosynthesis and salt tolerance both by directly trans-activating RrGGP2 and by synergizing with RrUNE12 through transcriptional activation and protein complex formation. These findings provide insights into the regulatory role of RrWRKY75 in abiotic stress tolerance and offer valuable genetic resources for R. roxburghii germplasm improvement.

Rosa↗
PubMed2026

Identification of the BrSK gene family in flowering Chinese cabbage and functional characterization of BrSK2 subfamily involvement in heat stress.

Glycogen synthase kinase 3 (GSK3) kinases are evolutionarily conserved regulators of plant development and stress signaling, yet their contributions to thermotolerance in cool-adapted Brassica crops remain poorly understood. Here, we identified 16 BrSK genes in the Caixin (Brassica rapa ssp. chinensis var. parachinensis) genome, all harboring intact catalytic motifs indicative of functional kinase activity. Spatiotemporal expression profiling revealed preferential accumulation of BrSK transcripts in stem apices and floral organs during reproductive transition, while promoter analysis identified abundant heat- and abiotic stress-responsive cis-elements. Under heat stress, BrSK21, BrSK22, and BrSK23 displayed striking genotype-specific expression dynamics. BrSK21/22/23 transcripts were stably suppressed in the heat-tolerant cultivar '49-19' but transiently declined before rapidly rebounding in the heat-sensitive 'Liuye 50', mirroring RNA-seq profiles. Protein-protein interaction assays (Y2H, BiFC, and LCI) demonstrated specific associations between BrSK kinases and BrHSFA1. Functional validation via VIGS revealed that silencing of BrSK21 significantly enhanced thermotolerance, with triple silencing of BrSK21/22/23 conferring additive protection, indicating functional redundancy within the BrSK2 subfamily. Collectively, these findings establish the BrSK2 subfamily as negative regulators of heat tolerance in Caixin, likely via modulation of BrHSFA1 expression. This work identifies high-priority targets for molecular breeding of climate-resilient Brassica vegetables.

Plant Proteins↗
PubMed2026

The combination of morphogenic regulators BABY BOOM and GRF-GIF improves maize transformation efficiency and promotes leaf regeneration.

Transformation is an indispensable tool for plant genetics and functional genomics. Although stable transformation in maize is no longer a major obstacle, there remains a need for accessible and efficient methods for academic laboratories. Here, we present the GGB system, a rapid and efficient approach optimized for immature embryo transformation in B104 and other maize lines. This system combines two distinct morphogenetic regulators, the wheat GRF4-GIF1 chimera and the maize BABY BOOM (BBM) transcription factor (hence the name "GGB") with a modified QuickCorn protocol, enabling regeneration of transformed maize plantlets in c. 2 months with an efficiency 7-fold higher than when compared to either morphogenic factor used in isolation. Expression of both regulators did not significantly affect development, eliminating the need to excise them after regeneration. However, transmission of the transgenic GGB construct through pollen was significantly reduced, potentially aiding transgenic line containment. We show that the GGB system is adaptable for CRISPR-Cas9 editing and reporter line generation. Furthermore, stable GGB transformants exhibited high leaf regeneration capacity via somatic embryogenesis. RNA-seq time-course profiling of GGB leaf cultures identified additional factors that could promote regeneration and led to the discovery of asparagine and trehalose as additional media components that significantly enhanced leaf regeneration.

Zea mays↗
PubMed2026

The circadian clock proteins PRR modulate root hair development via the RHD6/RSL module in Arabidopsis.

Root hairs, derived from trichoblasts, are critical for plant growth and environmental adaptation. Although environmental cues are known to influence root hair development, how endogenous timing systems such as the circadian clock integrate into the core transcriptional network governing root hair formation remains unclear. Here, we show that the circadian clock-associated protein PSEUDO-RESPONSE REGULATOR5 (PRR5) physically interacts with ROOT HAIR DEFECTIVE6 (RHD6) and RHD6 LIKE1 (RSL1), two basic helix-loop-helix transcription factors essential for root hair initiation. Genetic analyses suggest that PRR proteins contribute to root hair development under long-day conditions in Arabidopsis thaliana. Simultaneous disruption of PRR5, PRR7, and PRR9 results in defective root hairs, whereas PRR5 overexpression markedly increases root hair density and length. Transcriptomic and RT-qPCR analyses reveal that PRRs enhance the expression of RHD6, RSL1, and multiple downstream root hair-responsive genes, while modulating their temporal expression patterns. Furthermore, PRR5-mediated root hair promotion requires RHD6/RSL1, and PRR proteins enhance RHD6-dependent activation of the RSL4 promoter. PRRs also contribute to root hair development under phosphate-deficient and salt-stress conditions. Together, these findings establish a molecular framework in which PRR proteins regulate the RHD6/RSL network to coordinate root hair development and environmental responses.

Arabidopsis↗
PubMed2026

Contrasting redox-related physiological responses associated with HaGATA23 and HaGATA36 during Orobanche cumana parasitism in sunflower (Helianthus annuus L.).

Helianthus annuus is an economically important Asteraceae species used for seed oil production and ornamental purposes, but its production is seriously affected by the root-parasitic plant Orobanche cumana. GATA transcription factors are zinc-finger DNA-binding regulators involved in plant development and stress adaptation. However, the molecular characteristics of GATA transcription factors in Helianthus annuus and their contribution to Helianthus annuus -Orobanche cumana interaction remain poorly understood. Here, 36 HaGATA members were retrieved from the Helianthus annuus genome and classified into four phylogenetic clades. Chromosomal placement, collinearity, gene structure, motif composition, and promoter elements varied among the 36 HaGATA members, indicating evolutionary conservation coupled with functional diversification. Expression analysis and RT-qPCR analyses revealed differential expression patterns among HaGATA genes under O. cumana stress, with HaGATA23 markedly downregulated and HaGATA36 strongly upregulated. Overexpression of HaGATA23 was associated with increased malondialdehyde (MDA) accumulation and unfavorable changes in antioxidant enzyme activities, whereas its silencing showed the opposite physiological tendency. In contrast, overexpression of HaGATA36 reduced malondialdehyde accumulation, increased peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities, while its silencing showed the reverse tendency. These results indicate that HaGATA23 and HaGATA36 are candidate genes associated with contrasting redox-related physiological responses during O. cumana stress. This work provides evidence that GATA transcription factors are associated with redox-related physiological responses in sunflower under O. cumana treatment and identifies HaGATA23 and HaGATA36 as functionally divergent candidate genes for further validation.

Helianthus↗
PubMed2026

Comparative analysis of DDR-related genes and microRNA expression during rice germination: Implications for salinity susceptibility screening.

Soil salinity poses a significant threat to the agri-food sector and particularly to rice cultivation. High salinity during germination induces overproduction of reactive oxygen species (ROS) that cause lesions in the DNA resulting in reduced vigor. MicroRNAs (miRNAs) are known to modulate stress response in plants, however, studies focusing on its relation with the expression of the DNA damage response (DDR)-related genes are not thoroughly explored. In this regard, the aim of this work was to investigate the link between the expression of miRNAs and putative targeted DDR-related genes in response to salinity stress during germination. Eight varieties representative of indica and japonica rice subspecies were categorized into clusters through a principal component analysis (PCA) based on their germination performance and stress tolerance index under varying concentrations of NaCl. Subsequently, the expression patterns of six miRNAs and their putative targeted DDR genes were measured in two contrastive cultivars through quantitative real-time PCR (qRT-PCR) while correlations were examined through Pearson's analysis. Results showed distinct expression profiles between halotolerant and sensitive cultivars. Two miRNAs were further investigated in mature dry seeds of all the cultivars to verify their earliest, seed-specific discriminative potential. The distinct miR414 expression pattern may represent a potential biomarker for identifying salinity-susceptible cultivars during early-stage breeding screening.

Oryza↗
PubMed2026

Divergent trajectories of genome architecture and chromosome evolution in ferns and angiosperms.

Ferns and angiosperms represent the two largest vascular plant lineages but exhibit striking genomic and ecological contrasts. We investigated whether differences in genome size, chromosome architecture, GC content, and stomatal traits reveal divergent evolutionary trajectories between these lineages. We assembled the most comprehensive dataset to date, integrating genome size, chromosome number and size, GC content, and stomatal traits for over 1100 fern species and compared it with an extensive angiosperm dataset. Ferns exhibited markedly lower variability and c. 16-fold slower rates of chromosome size evolution than angiosperms. A persistent positive relationship between genome size and chromosome number in ferns suggests limited cytological post-polyploid diploidization. While ferns generally possess larger stomata, this difference disappears after accounting for genome size, indicating that nucleotypic constraints, rather than lineage-specific physiology, dictate stomatal dimensions. Both groups share a unimodal GC-genome size relationship peaking at c. 14 Gbp. Larger fern chromosomes imply lower genome-wide recombination rates, potentially limiting genetic reshuffling and adaptive potential. Our results highlight fundamentally divergent evolutionary trajectories, likely shaped by meiotic symmetry in ferns and meiotic asymmetry, possibly centromere drive, and post-polyploid diploidization in angiosperms, defining the functional and genomic landscapes of these lineages across deep evolutionary timescales.

Genome, Plant↗
PubMed2026

Phenotypic, physiological and transcriptomic analysis of graded salt stress responses in Pyrus betulifolia Bunge and functional characterization of the hub gene PbSTY46.

Pyrus betulifolia Bunge is a salt‑tolerant rootstock for pear, but its salt‑tolerance mechanisms remain largely unknown. In this study, P. betulifolia seedlings were subjected to graded NaCl stress at concentrations of 0 (CK), 50 (T1), 100 (T2), and 200 (T3) mM. We integrated phenotypic observation, physiological assessment, transcriptomic profiling, and functional gene validation to systematically elucidate its salt tolerance mechanisms. Salt stress inhibited seedling growth and root traits in a concentration-dependent manner, and T3 caused the most severe damage. Osmotic solutes responded differentially: soluble sugars peaked under T2, while proline peaked under T3. Antioxidant enzymes showed tissue-specific biphasic responses and declined after prolonged T3 stress. Meanwhile, chlorophyll and photosynthesis decreased, whereas anthocyanin increased, indicating a metabolic shift from photosynthesis to photoprotection. Transcriptome analysis revealed distinct responses depending on stress intensity: mild stress induced membrane lipid remodeling, moderate stress activated circadian rhythm and hormone signaling, and severe stress enhanced phenylpropanoid biosynthesis and thiamine metabolism. Gene Set Enrichment Analysis (GSEA) further highlighted progressive enrichment of phenylpropanoid biosynthesis, heme binding, and oxidoreductase activity. Weighted Gene Co‑expression Network Analysis (WGCNA) identified a blue module significantly positively correlated with root traits, from which the hub gene PbSTY46 was identified. Functional validation via overexpression, loss‑of‑function mutants, and pharmacological interventions (MeJA/DIECA) confirmed that PbSTY46 acts through JA signaling to enhance antioxidant enzyme activities and thereby confer salt tolerance. Collectively, P. betulifolia adopts a "survival‑first" strategy that coordinates growth arrest, osmotic homeostasis, and ROS scavenging. These findings establish PbSTY46 as a key regulator that links JA signaling to antioxidant defense. Thus, PbSTY46 represents a promising candidate for marker‑assisted breeding of salt‑tolerant pear cultivars.

Salt Stress↗
PubMed2026

Maize ZmMYB59 inhibits post-germinative shoot and root elongation through ZmGA2ox3/10-mediated gibberellin catabolism.

Gibberellin (GA) promotes seed germination, but sustained or excessive GA signaling after germination can lead to aberrant root and shoot elongation. How GA homeostasis is transcriptionally restrained during post-germinative seedling development remains unclear. Using overexpression and gene-edited maize materials, we demonstrate that ZmMYB59 inhibits root and shoot elongation during post-germinative growth. Integrated RNA-Seq and CUT&Tag analyses identified the GA catabolism genes ZmGA2ox3 and ZmGA2ox10 as candidate direct targets of ZmMYB59. Hormone profiling analysis showed elevated bioactive GA1 and GA4 levels in the scutellum and aleurone layer cells of zmmyb59 mutants. Dual-luciferase assays, electrophoretic mobility shift assays, and ChIP-qPCR further confirmed that ZmMYB59 directly binds AC8 cis-elements in the ZmGA2ox3/10 promoters and activates their transcription. The zmga2ox3/10 double mutant, but neither single mutant, exhibited enhanced root and shoot elongation, accompanied by GA4 accumulation. This phenotype was suppressed by exogenous application of the GA biosynthesis inhibitor uniconazole. Transcriptomic and biochemical analyses further revealed enhanced starch degradation, reduced starch content, and increased soluble sugar accumulation in the double mutant. Taken together, these findings reveal that the ZmMYB59-ZmGA2ox3/10 module restrains GA accumulation and starch mobilization after germination, thereby coordinating reserve utilization with post-germinative root and shoot growth in maize.

Gibberellins↗
PubMed2026

Efficient homologous replacement and deletion of large genomic fragments through template-jumping prime editing in rice.

Homologous replacement of genomic sequences with large DNA fragments (> 100 bp) holds great potential for crop breeding, yet an efficient method to achieve such edits is lacking in plants. Here, in rice, we developed template-jumping prime editing (TJ-PE), a recently reported PE strategy for large targeted insertion, as an efficient tool for homologous replacement with DNA fragments ranging from dozens to hundreds of base pairs, and using TJ-PE, we replaced genomic fragments of up to 340 bp with homologous fragments of the same length. In addition, our TJ-PE tool also enabled precise deletion of 944- to 2024-bp fragments in rice, with efficiencies of up to 34.6% for c. 2000-bp precise deletions. Collectively, this study expands the editing scope of PE in rice and establishes TJ-PE as a generalist tool for precise deletion and replacement of large DNA fragments.

Oryza↗
PubMed2026

Acetylcholine signaling regulates osmotic stress adaptation in the phytopathogen Dickeya solani.

Plants impose strong selective pressures that shape both the composition and functional potential of plant microbiomes. The adaptation of plant-associated bacteria to their hosts relies on an extensive repertoire of signal transduction systems that sense plant-derived molecules and dynamically adjust bacterial physiology and metabolism within the holobiont. These signals include key plant signaling compounds that regulate processes essential for plant-microbe interactions. Among them, acetylcholine is emerging as an important signaling molecule in both plants and bacteria. Here, we demonstrate that acetylcholine regulates the expression of the osmotic stress response betIBA gene cluster in the important phytopathogen Dickeya solani, where it plays an important role in osmoprotection. We show that the TetR-family transcriptional regulator associated with this pathway, BetIDs, recognizes acetylcholine as well as choline and trimethylamine. These three ligands differentially induce betIBA transcription in a manner that correlates with their binding affinities. Ligand binding does not affect BetIDs binding to the bet promoter or its oligomeric state. Instead, it induces pronounced changes in the secondary structure of BetIDs, with the magnitude of these conformational changes being ligand-dependent. We further show that quorum sensing modulates osmotic stress tolerance in D. solani by regulating the expression of the Bet pathway. The Bet system is required for the full virulence of D. solani, particularly in chemically complex plant tissues. Phylogenetic analyses reveal that the BetIBA system is widely distributed among plant-associated Pseudomonadota, collectively supporting its importance for bacterial survival and adaptation in plant-related environments.

Osmotic Pressure↗
PubMed2026

Integrated assessment of biocontrol potential and genome analysis of endophytic Bacillus velezensis MGL-B1 against mango stem-end rot.

Mango stem-end rot is a globally significant postharvest disease that severely threatens the mango industry, primarily caused by Botryosphaeria dothidea. However, information on biocontrol agents targeting this pathogen in mango remains limited. In this study, we isolated and identified a strain of Bacillus velezensis MGL-B1 from mango leaf tissues for the first time, which exhibited broad-spectrum antifungal activity. Both in vitro and in vivo assays demonstrated that MGL-B1 effectively inhibited the growth of B. dothidea, with an in vivo biocontrol efficacy reaching 83.72 ± 5.10%, comparable to that of the commonly used chemical fungicide thiabendazole. Further mechanistic analysis revealed that MGL-B1 acts by directly disrupting the integrity of the pathogen's mycelial cell membrane. In addition, its released volatile organic compounds (VOCs) also displayed significant antifungal activity, with components such as 2-nonanone, 2-nonanol, and phenylethyl alcohol being confirmed to exert antifungal effects in in vitro fumigation assays. qPCR analysis showed that MGL-B1 treatment significantly upregulated the transcriptional levels of genes involved in plant-pathogen interaction, phenylpropanoid biosynthesis, and antioxidant defense pathways in mango fruits, with upregulation folds of 16.32, 37.19, and 75.93, respectively; meanwhile, the expression of browning-related genes such as polyphenol oxidase (PPO) was markedly suppressed. Whole-genome sequencing further revealed 14 biosynthetic gene clusters for antimicrobial compounds, including five unknown gene clusters. Collectively, B. velezensis MGL-B1 represents a promising biocandidate strain with multiple antifungal mechanisms and excellent control efficacy, providing a valuable resource for green and sustainable management of mango diseases.

Mangifera↗
PubMed2026

Distinct cell morphotypes of Aureobasidium melanogenum ZN exhibit differential functional profiles in promoting maize growth.

Black yeast-like fungi of the genus Aureobasidium exhibit morphological plasticity, but whether distinct cellular states within the same genetic background are associated with different plant growth-promoting functions remains unclear. Here, yeast-like cells (YL), swollen cells (SC), and chlamydospores (CH) of Aureobasidium melanogenum ZN were characterized. YL was associated mainly with siderophore production and laccase activity, SC with extracellular polysaccharide accumulation, and CH with phosphate mobilization and higher ammonia and IAA production. Whole-genome and comparative genomic analyses revealed a shared repertoire related to nutrient acquisition, auxin-associated metabolism, extracellular oxidation, and carbohydrate remodeling, with expansions in nutrient- and cell-surface-related gene families. Transcriptomic and metabolomic analyses showed distinct deployment of these capacities, with CH exhibiting broad reprogramming of tryptophan-associated, nitrogen, phosphate, central-carbon, and amino-acid metabolism. In maize, CH at the optimal inoculation concentration of 105 CFU·mL-1 produced the strongest growth promotion, increasing plant height, dry biomass, root length, root surface area, and root volume by 58.6%, 365.1%, 191.0%, 194.3%, and 222.4%, respectively. Consistent with this pronounced growth phenotype, maize root transcriptomics showed coordinated CH-induced responses involving root development, nutrient transport, redox regulation, and root-interface remodeling. Root-zone tracking showed greater short-term stability and persistence of CH. These findings identify cellular state as an important functional dimension of Aureobasidium-plant interactions and provide a basis for developing fungal inoculants with defined beneficial cellular states.

Zea mays↗
PubMed2026

Phosphorus modulates starch granule development and metabolic partitioning in wheat grain: Insights from SGAP proteomics and nutrition and processing quality.

This study investigates how phosphorus (P) levels are associated with carbon-nitrogen metabolism in wheat grains. Optimal P application (105 kg P₂O₅ ha⁻¹) was associated with enhanced pericarp-endosperm coordination, increased carbon allocation to the endosperm, and early B‑type starch granule formation. Starch granule‑associated protein (SGAP) proteomics showed that optimal P upregulated cytoskeletal and starch‑synthesis proteins bound to starch granules in the endosperm, while reducing storage protein degradation‑related SGAPs in the pericarp. These metabolic adjustments were correlated with increased grain‑filling intensity and duration, and were associated with the highest theoretical grain weight (50.70 mg). Furthermore, optimal P was associated with enrichment of amino acid biosynthesis pathways and with higher levels of essential amino acids (e.g., lysine and threonine by 17.0--26.8%) and an improved essential amino acid profile without altering total protein content. In contrast, excessive P (210 kg P₂O₅ ha⁻¹) was associated with disrupted inter‑tissue coordination but did not simply impair grain filling; instead, HP corresponded to a unique developmental program: it was linked to an early burst of C‑type starch granules (0∼5 µm) at 7 DPA, yet by maturity achieved the highest proportion of large A‑type granules (56.8%) and the highest total starch content (63.5%), together with elevated endosperm phosphorus at 14 DPA and enrichment of spliceosome‑related pathways. HP also showed higher levels of several functional amino acids (glutamate, cysteine, histidine, proline) compared to P0. However, HP was associated with a higher gliadin/globulin ratio and did not improve grain yield. These findings suggest that phosphorus supply is associated with grain quality through tissue‑specific metabolic reprogramming, and that precision management-rather than maximized application-warrants consideration for optimizing both yield and processing quality.

Triticum↗
PubMed2026

Integrated metabolomic, transcriptomic, and proteomic analyses reveal changes in the non-volatile metabolite profile of LED light-withered oolong tea.

LED light withering is a crucial method for overcoming weather limitations and enhancing the quality of oolong tea. To elucidate the underlying molecular mechanisms, this study simulated solar spectra using multiwavelength LED light and compared the resulting metabolic, transcriptomic, and proteomic profiles during the enzymatic-catalysis process (ECP) in oolong tea processing. Results indicated that LED light withering altered gene expression and protein regulation of secondary metabolism, particularly in the flavonoid biosynthesis pathway. These shifts encompassed key quality-related compounds, including flavonoids (quercetin-3-O-rhamnoside, dihydroquercetin), amino acids (L-asparagine, L-histidine), guanosine 5'-monophosphate (GMP), and carbohydrates. Furthermore, LED light withering accelerated tea leaf water loss, influenced gene expression involved in photosynthetic cellular components (chloroplasts, thylakoids), increased ascorbate peroxidase regulation under stress, and subsequently modulated energy metabolism and signal transduction in tea leaves. This study offers molecular theoretical framework for the controlled light-withering of oolong tea under bad weather and the associated improvements in its quality.

Camellia sinensis↗
PubMed2026

Free polyphenols and multi-omics traits underlying antioxidant variation across Paeonia lactiflora leaf cultivars.

Leaves of Paeonia lactiflora are underutilized by-products with potential as natural antioxidant sources. In this study, 18 cultivars were evaluated for phytochemical composition and in vitro antioxidant capacity. Total phenolic content correlated strongly with DPPH and ABTS activities, and the comprehensive antioxidant index identified 'Coral Charm' and 'Hangshao' as representative high- and low-antioxidant cultivars, respectively. Untargeted metabolomics detected 2677 metabolites and identified 908 differential metabolites between the two cultivars. Targeted phenolic profiling quantified 27 compounds, among which 11 differed significantly between the two cultivars. Catechin and epicatechin were enriched in 'Coral Charm', with contents of 6.62 and 0.397 ng/mg, respectively, compared with 0.012 and 0.002 ng/mg in 'Hangshao'. (+)-Dihydroquercetin was also more abundant in 'Coral Charm', while caffeic acid showed an upward trend. Proteomic analysis identified 423 differentially expressed proteins, mainly associated with secondary metabolite biosynthesis, redox homeostasis, and central carbon metabolism. Integrated analysis identified pyruvate metabolism as the only pathway significantly enriched in both metabolomic and proteomic datasets. Molecular docking predicted favorable binding between representative phenolics and selected proteins. These findings link cultivar-dependent antioxidant variation in peony leaves with free-phenolic accumulation and pathway-level metabolic differences, supporting the selection and utilization of antioxidant-rich peony leaf resources.

Antioxidants↗
PubMed2026

The cold case of state transition 7 (stt7) mutants of Chlamydomonas reinhardtii, solved by whole-genome sequencing.

The process of State Transitions (ST) corresponds to an STT7 kinase-driven redistribution of the transmembrane LHCII antenna proteins between Photosystem II (PSII) and Photosystem I (PSI), which results from changes in their phosphorylation state. For the past two decades, two LHCII-kinase mutants, stt7-1 and stt7-9, have been instrumental in the study of STs in Chlamydomonas reinhardtii, the former being a null mutant for the kinase but quasi-sterile in crosses, while the latter, although fertile, has a leaky phenotype. Using long-read sequencing, this study further characterized the genetic lesions of the stt7 mutant strains through whole-genome reconstruction and de novo chromosome assembly. In addition, two new stt7 null mutants were generated, one derived by crosses from the original stt7-1 and one obtained by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated protein 9 (Cas9) technology. This work provides a comprehensive genomic characterization of the original stt7-1 null mutant, revealing extensive chromosomal rearrangements and high levels of aneuploidy, associated with increased cell size and meiotic dysfunction. Reassessment of their physiology and genetic backgrounds highlights the need for caution in interpreting genetic information. We thus produced more reliable null mutants for the LHCII-kinase, amenable to genetic crosses for the study of STs in a variety of genetic backgrounds.

Chlamydomonas reinhardtii↗