Laura Valverde | Search PubMed

PubMed2026

DNA-binding activity of PIF7 links phytochrome B signaling to plant responses to vegetation proximity.

PHYTOCHROME INTERACTING FACTORs (PIFs) are transcription factors that act as central signaling hubs in light-regulated processes. All PIFs contain an active phytochrome B-binding motif and a DNA-binding basic helix-loop-helix domain. In the shade-avoider Arabidopsis thaliana, PIF7 is a major promoter of hypocotyl elongation in response to vegetation proximity, becoming active when released from phytochrome B via its active phytochrome B-binding motif. Here we show that PIF7 promotes seedling elongation in other species, including the shade-avoider tomato and the shade-tolerant Cardamine hirsuta, suggesting that PIF7 has retained some of its key functional domains across diverse plants. Through complementation analyses using PIF7 variants lacking either the active phytochrome B-binding or basic helix-loop-helix domain, we demonstrate that, unlike PIF3, PIF7 versions unable to bind phytochrome B remain active regardless of light conditions, whereas loss of DNA-binding capacity fully disrupts PIF7 function. Our results further suggest that phytochrome B interaction imposes a dual regulatory control over PIF7, modulating both its abundance and its phosphorylation state (ie its ability to bind and regulate target genes).

Phytochrome B↗

PubMed2025

A melon (Cucumis melo) homologue of REPRESSOR OF PHOTOSYNTHETIC GENES prevents chloroplast differentiation in the fruit flesh.

Fruit flesh color in melon can be orange, green or white, depending on the accumulation of the orange carotenoid β-carotene or / and green chlorophylls. The dominant allele of Green flesh (Gf) causes orange melons, but in the absence of this allele the flesh of ripe melon can be white or green depending on the White flesh (Wf) locus, being white dominant over green. The identity of Wf has remained unclear despite several candidates have been proposed. Here we identified Wf by fine mapping of a segregating population derived from the white-fleshed variety Piel de Sapo (PS, gf gf / Wf Wf) and the orange-fleshed Védrantais (VED, Gf Gf / wf wf). Wf corresponds to the gene MELO3C003098, herein referred to as CmRPGE1 as it encodes a fruit-specific homologue of REPRESSOR OF PHOTOSYNTHETIC GENES (RPGE) microproteins. Similar to RPGE homologues from other plants, overexpression of the PS allele (CmRPGE1 PS ) caused a pale green leaf phenotype in Nicotiana benthamiana and Arabidopsis thaliana. By contrast, a 10-nucleotide deletion in the VED allele (CmRPGE1 VED ) resulted in a loss of RPGE function. The active CmRPGE1PS microprotein interacts with a fruit-localized melon homologue of ARABIDOPSIS PSEUDO-RESPONSE REGULATOR2 (APRR2), a GARP family transcription factor. Binding of CmRPGE1PS retains the melon APRR2 homologue in the cytosol, hence preventing the regulation of target genes involved in chloroplast biogenesis. In green fruit cultivars, the non-functional CmRPGE1VED allele allows APRR2 to perform its function, leading to chloroplast development and consequently a green flesh phenotype.

Biological Sciences – Plant Biology↗