Out of the blue: Phototropins of the leaf vascular bundle sheath mediate the regulation of leaf hydraulic conductance by blue light

Yael Grunwald, Sanbon Chaka Gosa, Tanmayee Torne-Srivastava, Nava Moran, Menachem Moshelion*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

The Arabidopsis (Arabidopsis thaliana) leaf veins bundle-sheath cells (BSCs) - a selective barrier to water and solutes entering the mesophyll - increase the leaf radial hydraulic conductance (Kleaf) by acidifying the xylem sap by their plasma membrane H+-ATPase, AHA2. Based on this and on the BSCs' expression of phototropins PHOT1 and PHOT2, and the known blue light (BL)-induced Kleaf increase, we hypothesized that, resembling the guard cells, BL perception by the BSCs' phots activates its H+-ATPase, which, consequently, upregulates Kleaf. Indeed, under BL, the Kleaf of the knockout mutant lines phot1-5, phot2-1, phot1-5 phot2-1, and aha2-4 was lower than that of the wild-type (WT). BSC-only-directed complementation of phot1-5 or aha2-4 by PHOT1 or AHA2, respectively, restored the BL-induced Kleaf increase. BSC-specific silencing of PHOT1 or PHOT2 prevented such Kleaf increase. A xylem-fed kinase inhibitor (tyrphostin 9) replicated this also in WT plants. White light - ineffective in the phot1-5 mutant - acidified the xylem sap (relative to darkness) in WT and in the PHOT1-complemented phot1-5. These results, supported by BL increase of BSC protoplasts' water permeability and cytosolic pH and their hyperpolarization by BL, identify the BSCs as a second phot-controlled water conductance element in leaves, in series with stomatal conductance. Through both, BL regulates the leaf water balance.

Original languageAmerican English
Pages (from-to)2328-2342
Number of pages15
JournalPlant Cell
Volume34
Issue number6
DOIs
StatePublished - Jun 2022

Bibliographical note

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© 2022 American Society of Plant Biologists. All rights reserved.

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