Badiger, B. G. | Search bioRxiv

bioRxiv2022

Natural variation identifies new effectors of water use efficiency in Arabidopsis.

Water use efficiency (WUE) is the ratio of biomass gained per unit of water consumed; thus, it can be altered by genetic factors that affect either side of the ratio. In the present study, we exploited natural variation for WUE as an unbiased approach to discover loci affecting either biomass accumulation or water use as factors affecting WUE. Genome-wide association (GWAS) analysis using integrated WUE measured through carbon isotope discrimination ({delta}13C) of Arabidopsis thaliana accessions identified genomic regions associated with WUE. Reverse genetic analysis of 70 candidate genes selected based on the GWAS results and transcriptome data identified 25 genes affecting WUE as measured by gravimetric and {delta}13C analyses. Mutants of four genes had higher WUE than wild type, while mutants of the other 21 genes had lower WUE. The differences in WUE were caused by either altered biomass or water consumption (or both). Stomatal density was not a primary cause of altered WUE in these mutants. Leaf surface temperatures indicated that transpiration differed for mutants of 16 genes, but generally biomass accumulation had greater effect on WUE. The genes we identified are involved in diverse cellular processes including hormone and calcium signaling, meristematic activity, photosynthesis, flowering time, leaf/vasculature development, and cell wall composition; however, none of them had been previously linked to WUE or traits related to plant water relations. Thus, our study successfully identified new effectors of WUE that can be used to understand the genetic basis of WUE and improve crop productivity.

plant biology↗

bioRxiv2021

Spatial differences in stoichiometry of EGR phosphatase and Microtubule-Associated Stress Protein 1 control root meristem activity during drought stress.

During moderate severity drought and low water potential ({psi}w) stress, poorly understood signaling mechanisms restrict both meristem cell division and subsequent cell expansion. We found that the Clade E Growth-Regulating 2 (EGR2) protein phosphatase and Microtubule Associated Stress Protein 1 (MASP1) differed in their stoichiometry of expression across the root meristem and had opposing effects on root meristem activity at low {psi}w. Ectopic MASP1 or EGR expression increased or decreased, respectively, root meristem size and root elongation during low {psi}w stress. This, along with the ability of phosphomimic MASP1 to overcome EGR suppression of root meristem size and observation that ectopic EGR expression had no effect on unstressed plants, indicated that during low {psi}w EGR activation and attenuation of MASP1 phosphorylation in their overlapping zone of expression determines root meristem size and activity. Ectopic EGR expression also decreased root cell size at low {psi}w. Conversely, both the egr1-1egr2-1 and egr1-1egr2-1masp1-1 mutants had similarly increased root cell size; but, only egr1-1egr2-1 had increased cell division. These observations demonstrated that EGRs affect meristem activity via MASP1 but affect cell expansion via other mechanisms. Interestingly, EGR2 was highly expressed in the root cortex, a cell type important for growth regulation and environmental response. One Sentence SummarySpatial differences in EGR-MASP1 expression and control of MASP1 phosphorylation adjust root meristem activity to regulate growth during drought stress. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantcell.org) is: Paul E. Verslues (paulv@gate.sinica.edu.tw).

plant biology↗