At14a-Like1 participates in membrane-associated mechanisms promoting growth during drought in Arabidopsis thaliana

Abstract

Limited knowledge of how plants regulate their growth and metabolism in response to drought and reduced soil water potential has impeded efforts to improve stress tolerance. Increased expression of the membrane-associated protein At14a-like1 (AFL1) led to increased growth and accumulation of the osmoprotective solute proline without negative effects on unstressed plants. Conversely, inducible RNA-interference suppression of AFL1 decreased growth and proline accumulation during low water potential while having no effect on unstressed plants. AFL1 overexpression lines had reduced expression of many stress-responsive genes, suggesting AFL1 may promote growth in part by suppression of negative regulatory genes. AFL1 interacted with the endomembrane proteins protein disulfide isomerase 5 (PDI5) and NAI2, with the PDI5 interaction being particularly increased by stress. PDI5 and NAI2 are negative regulatory factors, as pdi5, nai2, and pdi5-2nai2-3 mutants had increased growth and proline accumulation at low water potential. AFL1 also interacted with Adaptor protein2-2A (AP2-2A), which is part of a complex that recruits cargo proteins and promotes assembly of clathrin-coated vesicles. AFL1 colocalization with clathrin light chain along the plasma membrane, together with predictions of AFL1 structure, were consistent with a role in vesicle formation or trafficking. Fractionation experiments indicated that AFL1 is a peripheral membrane protein associated with both plasma membrane and endomembranes. These data identify classes of proteins (AFL1, PDI5, and NAI2) not previously known to be involved in drought signaling. AFL1-predicted structure, protein interactions, and localization all indicate its involvement in previously uncharacterized membrane-associated drought sensing or signaling mechanisms.E ven relatively mild drought that causes reduced soil water potential (ψ w ) can result in dramatically reduced plant growth and agricultural productivity. Physiological analyses have shown that plant growth is actively down-regulated during drought and is not limited by carbon supply (1-3). Reductions of growth help ensure survival by conserving water but can be undesirable for agriculture, as plant productivity is reduced more than need be if growth were less sensitive to changes in water status (3). Also, specific metabolic pathways, such as proline metabolism, are stress regulated and contribute to drought tolerance.The sensing and signaling mechanisms controlling growth and metabolic responses to drought remain unclear. Many hypotheses of how plants sense water loss center on detection of mechanical stimuli generated by loss of turgor and cell shrinkage. This includes changes in membrane shape or disruption of cell wall-cell membrane connections possibly detected by proteins, such as mechanosensitive channels or receptor-like kinases that bind cell wall components (4-9). Proteins that induce or detect membrane curvature are known in mammalian cells (10) but have been little considered in plants. Also, in analogy to mammal...

A Family of NAI2-Interacting Proteins in the Biogenesis of the ER Body and Related Structures

“…TSA1 also interacts with CSN1, one of the subunits of the COP9 signalosome, which participates in diverse cellular and developmental processes (Li et al, 2011). NAI2 interacts with AFL1, a peripheral membrane protein associated with both plasma membrane and endomembranes (Kumar et al, 2015). The interactions of NAI2 and TSA1 with these proteins were demonstrated not only by yeast two-hybrid assays but also by BiFC and coimmunoprecipitation (Figs.…”

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De novogenome assembly and transcriptome analysis for the drought and salt resistantSolanum sitiens

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