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PubMed1991

Tissue-specific and organ-specific expression of soybean auxin-responsive transcripts GH3 and SAURs.

We used in situ hybridization to localize two classes of auxin-regulated transcripts, GH3 and SAURs, within organs and tissues of soybean seedlings and flowers. GH3 transcripts occurred in the inner cortex and protoxylem ridges of roots and were expressed transiently during flower and pod development. SAUR transcripts were expressed in the epidermis, cortex, and starch sheath of epicotyls and immature hypocotyls. SAUR transcripts became more abundant on the bottom side of hypocotyls that were undergoing gravitropic curvature. SAURs were also expressed in developing xylem elements of the hypocotyl hook. When soybean organ sections were treated with 50 micromolar 2,4-dichlorophenoxyacetic acid (2,4-D), GH3 transcripts became more abundant in the vascular regions of all organs analyzed. High levels of GH3 transcripts were also found in developing palisade mesophyll cells of leaves, cotyledons, and flowers treated with 2,4-D. SAUR transcripts became more abundant in the epidermis, cortex, starch sheath, and pith of epicotyls and hypocotyls after 2,4-D treatment. Our results showed that a variety of tissues and cell types express auxin-responsive transcripts and that different tissues respond rapidly to exogenous auxin by expressing different hormone-responsive genes.

Gene Expression Regulation↗

PubMed1991

Comparative localization of three classes of cell wall proteins.

The localization of the cell wall proline-rich proteins (PRPs), and the gene expression of the cell wall glycine-rich proteins (GRPs) and the hydroxyproline-rich glycoproteins (HRGPs) were examined in several dicot species. The PRPs are accumulated in the corner walls of the cortex where several cells are joined together and in the protoxylem cell walls of 3-day-old soybean root. In 1-month-old soybean plants, the PRPs are specifically deposited in xylem vessel elements of the young stem, and they are accumulated in both phloem fibers and xylem vessel elements and fibers of the older stem. Likewise, the PRPs are localized in xylem vessel elements and fibers in tomato, petunia, potato and tobacco stems. They are also found in outer and inner phloem fiber cell walls of tomato stem and in outer phloem fiber cell walls of petunia stem. The gene expression of the HRGPs and the GRPs is developmentally regulated in tomato, petunia and tobacco stems. HRGP mRNAs are abundant in outer and inner phloem regions, while GRP mRNAs are present mostly in primary xylem and in the cambium region. Immunocytochemical localization showed that the GRPs have a localization pattern similar to that of the PRPs in tomato, petunia and tobacco stems.

Amino Acid Sequence↗

PubMed1978

Adhesion of Bacteroides succinogenes in pure culture and in the presence of Ruminococcus flavefaciens to cell walls in leaves of perennial ryegrass (Lolium perenne).

Bacteroides succinogenes and Ruminococcus flavefaciens are two of the most important cellulolytic bacteria in the rumen. Adhesion of B. succinogenes in pure culture, and in mixed culture with R. flavefaciens, to the various types of cell walls in sections of perennial ryegrass (Lolium perenne L. cultivar S24) leaves was examined by transmission and scanning electron microscopy. B. succinogenes adhered to the cut edges of most plant cell walls except those of the meta- and protoxylem. It also adhered, though in much smaller numbers, to the uncut surfaces of mesophyll, epidermal, and phloem cell walls. In mixed culture, both species adhered in significant numbers to the cut edges of most types of plant cell wall, but R. flavefaciens predominated on the epidermis, phloem, and sclerenchyma cell walls. B. succinogenes predominated on the cut edges and on the uncut surfaces of the mesophyll cell walls, and its ability to adhere to uncut surfaces of other cell walls was not affected by the presence of the ruminococcus. Both organisms rapidly digested the epidermal, mesophyll, and phloem cell walls. Zones of digestion were observed around bacteria of both species when attached to the lignified cell walls of the sclerenchyma, but not when attached to the lignified xylem vessels.

Adhesiveness↗

PubMed1977

Ultrastructural localization of acid phosphatase activity in root tips by the p-(acetoxymercuric) aniline diazotate reagent and a comparison with a Gomori procedure.

The localization of acid phosphatase was studied in root tip cells of pea and mung bean by use of a heavy metal azo-dye technique. Diazotized p-(acetoxymercuric) aniline in a post-coupling procedure, using naphthol AS-BI phosphate as substrate, yielded a fine particulate reaction product within vacuoles, intercellular spaces, multivesicular bodies and at various sites throughout the cytoplasm of pea root cells and differentiating mung bean protoxylem cells. An ultrastructural comparison with a modified Gomori lead-salt precipitation method revealed differences in the subcellular location of beta-glycerophosphatase and naphthol AS-BI phosphatase. The distribution of acid phosphatases within plant meristematic cells is discussed.

Acid Phosphatase↗

PubMed2026

Zea mays Drought-Overly Sensitive1/TUBA4 Is Wilty3, and Transcriptome Co-Expression Analysis of Shoot Meristem Mutant Tissues Reveals Wilty2/TUB6:Wi3 Interactions Associated With Stem Vascular Bundle Development.

Plant vasculature is essential for the transport of water, nutrients, and signaling molecules across organs, while also providing critical mechanical support for growth and development. Disruptions in vascular bundle formation can therefore lead to severe physiological and developmental defects. In maize, ethyl methanesulfonate (EMS)-induced dominant nonallelic Wilty mutants exhibit a pronounced wilting phenotype even under well-watered conditions, indicating underlying defects in vascular function. In this study, we characterized the Wi3 mutant, identified as ZmDrought-Overly-Sensitive1/DOS1, and compared it with the previously described Wi2 mutant to uncover shared mechanisms underlying their phenotypes. We provide evidence, by bulk segregant resequencing linkage disequilibrium of SNPs adjacent to the causal Wilty SNPs in respective ß- and α-tubulin genes, for the personal communication from Gerry Neuffer that Wi2/ß-tub6 provenance is from ACR-related stock, whereas Wi3/α-tub4 allele is from Mo17, not B73 as claimed by the authors who cloned Dos1. Histochemical staining and Fourier-transform infrared (FTIR) spectroscopy of vascular bundles in Wi3 indicated apparent alterations in cellulose and lignin content consistent with those observed in Wi2. Transcriptome analysis of shoot meristems further indicated that similar sets of genes and pathways are differentially expressed in both mutants, suggesting convergence on common biological pathways. Using bulk-segregant whole-genome resequencing, we identified alpha-tubulin4 (TUA4) as the causal gene in Wi3 (ZmDOS1), harboring a C-to-T substitution within the N-terminal GTPase-binding domain. This mutation results in a glutamic acid196-to-lysine substitution. Given that α- and β-tubulin subunits heterodimerize, and in many plants and animal mutant alleles are dominant-negative gains-of-function, we infer Wi2, Wi3, and likely Wi4, based on very similar FTIR biophysical difference spectra, may act as effectors of vascular bundle cell wall deposition, potentially involving vesicle trafficking as recently shown for asymmetric cell divisions in maize stomatal development. Together, these findings highlight the functional interdependence of tubulin subunits and provide a plausible mechanistic framework for the striking biophysical, transcriptomic, and phenotypic similarities observed between Wi2, Wi3/ZmDOS1, and Wi4 mutants.

bulk segregant analysis↗