Shackel, K. A. | Search bioRxiv

bioRxiv2022

A suberized exodermis is required for tomato drought tolerance

Plant roots integrate environmental signals and developmental programs using exquisite spatiotemporal control. This is apparent in the deposition of suberin, an apoplastic diffusion barrier, which regulates the entry and exit of water, solutes and gases, and is environmentally plastic. Suberin is considered a hallmark of endodermal differentiation, but we find that it is absent in the tomato endodermis during normal development. Instead, suberin is present in the exodermis, a cell type that is absent in the model organism Arabidopsis thaliana. Here, we uncover genes driving exodermal suberization and describe its effects on drought responses in tomato, unravelling the similarities and differences with the paradigmatic Arabidopsis endodermis. Cellular resolution imaging, gene expression, and mutant analyses reveal loss of this program from the endodermis, and its co-option in the exodermis. Functional genetic analyses of the tomato MYB92 transcription factor and ASFT enzyme demonstrate the importance of exodermal suberin for a plant water-deficit response. Controlling the degree of exodermal suberization could be a new strategy for breeding climate-resilient plants.

plant biology↗

bioRxiv2019

Minimally invasive, pressure probe based sampling allows for in-situ gene expression analyses in plant cells.

BackgroundGene expression analyses are conducted using multiple approaches and increasingly research has been focused on assessing gene expression at the level of a tissue or even single-cells. To date, methods to assess gene expression at the single-cell in plant tissues have been semi-quantitative, require tissue disruption, and/or involve laborious, possibly artifact-inducing manipulation. In this work, we used grape berries (Vitis vinifera L. Zinfandel) as a model in order to examine the validity and reproducibility of an in-situ gene expression analysis method combining a cell pressure probe (CPP) with quantitative PCR (qPCR).\n\nResultsWe developed a method to directly assess gene expression levels via qPCR from cellular fluids sampled in-situ with a CPP. Cellular fluids, with volumes in the picoliter range, were collected from intact berries with a CPP at various depths across skin and mesocarp tissues. The expression of a key anthocyanin biosynthetic gene, UDP-glucose: flavonoid 3-O-glucosyltransferase (VviUFGT), was analyzed as a test case since its expression is restricted to cells producing anthocyanins in grape berry skins during ripening. The method identifies samples contaminated with significant levels of genomic DNA by amplifying a region of VviUFGT that spans an intron. Therefore false positives were discarded which occurred in 28% of the samples tested. Shallow probing of skin cells showed high VviUFGT expression as expected while deeper probing of mesocarp cells resulted in no VviUFGT expression.\n\nConclusionsThe clear correspondence of VviUFGT expression to the targeted cell samples suggests that the in-situ gene expression analysis using a CPP is reliable and does not result in contamination as the probe moves through tissues. This method can be paired to single-cell transcriptomic analyses in the future. We conclude that this technique represents a minimally invasive method of sampling plant cells in-situ which creates an opportunity for the analysis of cellular level, spatiotemporal responses in heterogeneous plant tissues.

plant biology↗