The role of PLDα1 in providing specificity to signal‐response coupling by heterotrimeric G‐protein components in Arabidopsis

Abstract

SUMMARYHeterotrimeric G-proteins comprised of Ga, Gb and Gc subunits are important signal transducers in all eukaryotes. In plants, G-proteins affect multiple biotic and abiotic stress responses, as well as many developmental processes, even though their repertoire is significantly limited compared with that in metazoan systems. One canonical and three extra-large Ga, 1 Gb and 3 Gc proteins represent the heterotrimeric G-protein complex in Arabidopsis, and a single regulatory protein, RGS1, is one of the few known biochemical regulators of this signaling complex. This quantitative disparity between the number of signaling components and the range of processes they influence is rather intriguing. We now present evidence that the phospholipase Da1 protein is a key component and modulator of the G-protein complex in affecting a subset of signaling pathways. We also show that the same G-protein subunits and their modulators exhibit distinct physiological and genetic interactions depending on specific signaling and developmental pathways. Such developmental plasticity and interaction specificity likely compensates for the lack of multiplicity of individual subunits, and helps to fine tune the plants' responses to constantly changing environments.

Extra Large G-Protein Interactome Reveals Multiple Stress Response Function and Partner-Dependent XLG Subcellular Localization

“…Phospholipase D (PLD) is involved in the osmotic stress response through hydrolysis of phosphatidic acid (PA), the ABA signaling pathway (Jacob et al, 1999) and the biosynthesis of proline (Thiery et al, 2004). PDLα 1 interacts with GPA1 (Thiery et al, 2004) and AtRGS1 (Choudhury and Pandey, 2016), and the product of PLDα1, phosphatidic acid, may slightly inhibit the GAP activity of AtRGS1 (Choudhury and Pandey, 2017). …”

Phosphatidic acid plays key roles regulating plant development and stress responses

“…PLDα1 interacts with RGS1 (regulator of G‐protein signaling) and primarily acts as a GAP (GTPase‐activity accelerating protein) for Gα protein GPA1. RGS1 likely inhibits the GAP activity of PLDα1 in regulating ABA‐mediated responses (Zhao and Wang ; Choudhury and Pandey ). RGS1 and PLDα1 regulate each other in a bidirectional manner.…”

Phospholipases as GTPase activity accelerating proteins (GAPs) in plants

“…It is clear from our data that distinct regulatory modes are operative when comparing phenotypes such as leaf shape, hypocotyl length and ABA sensitivity, to primary root length, lateral root density, stomatal development and silique shapes. 14 …”

“…14 For example, both RGS1 and PLDa1 accelerate the GTPase activity of GPA1, RGS1 also inhibits the activity of PLDa1, and GPA1 affects the activity of PLDa1.…”

“…Our recent work and some of the work previously published by the Wang group establishes PLDa1 as one such GAP in plants. 14,15 We have recently shown, based on genetic and biochemical data that both RGS1 and PLDa1 act as efficient GAPs for Arabidopsis GPA1.…”