G-protein α-subunit (GPA1) regulates stress, nitrate and phosphate response, flavonoid biosynthesis, fruit/seed development and substantially shares GCR1 regulation in A. thaliana

Abstract

Heterotrimeric G-proteins are implicated in several plant processes, but the mechanisms of signal-response coupling and the roles of G-protein coupled receptors in general and GCR1 in particular, remain poorly understood. We isolated a knock-out mutant of the Arabidopsis G-protein α subunit (gpa1-5) and analysed its transcriptome to understand the genomewide role of GPA1 and compared it with that of our similar analysis of a GCR1 mutant (Chakraborty et al. 2015, PLoS ONE 10(2):e0117819). We found 394 GPA1-regulated genes spanning 79 biological processes, including biotic and abiotic stresses, development, flavonoid biosynthesis, transcription factors, transporters and nitrate/phosphate responses. Many of them are either unknown or unclaimed explicitly in other published gpa1 mutant transcriptome analyses. A comparison of all known GPA1-regulated genes (including the above 394) with 350 GCR1-regulated genes revealed 114 common genes. This can be best explained by GCR1-GPA1 coupling, or by convergence of their independent signaling pathways. Though the common genes in our GPA1 and GCR1 mutant datasets constitute only 26% of the GPA1-regulated and 30% of the GCR1-responsive genes, they belong to nearly half of all the processes affected in both the mutants. Thus, GCR1 and GPA1 regulate not only some common genes, but also different genes belonging to the same processes to achieve similar outcomes. Overall, we validate some known and report many hitherto unknown roles of GPA1 in plants, including agronomically important ones such as biotic stress and nutrient response, and also provide compelling genetic evidence to revisit the role of GCR1 in G-protein signalling.

Altered Expression of OsNLA1 Modulates Pi Accumulation in Rice (Oryza sativa L.) Plants

“…For example, overexpression of miRNA444a in rice plants, an Pi-starvation-inducible gene, led to the activation of nitrate signaling pathway only under Pi-starvation conditions, which resulted in transgenic plants to produce longer primary roots with fewer lateral roots compared to wild-type (Yan et al, 2014). Similarly, the transcriptome analysis of gpa1-5 mutant which exhibited several developmental phenotypes including the presence of longer roots with fewer lateral roots also revealed the induction of several nitrate starvation/assimilation genes such as NRT2.1, ICDH , and ASN1 and reduction of phosphate use efficiency genes such as WRKY75, PHT1 , and LPR1 compared to wild-type (Chakraborty et al, 2015). Remarkably, the development of primary root under Pi deficient conditions was found to be largely dependent on the presence of nitrate in the growth medium, which is suppressed by nitrate-inducible HRS1 and HHO1 transcription factors (Medici et al, 2015).…”

Root Cell-Specific Regulators of Phosphate-Dependent Growth

“…WDD1 encodes a transducin/ WD40 repeat-like protein annotated as a putative b-subunit of a heterotrimeric G-protein complex. Recently, G-protein-mediated signaling was associated with the WRKY75-dependent regulation of PSI genes (Chakraborty et al, 2015). This could explain the high impact of the knockout of WDD1 on yellow and red coexpression modules in P-limited roots, two modules that are largely associated with processes involved directly in Pi signaling and Pi homeostasis.…”

Metabolic profiling reveals glucose and fructose accumulation in gcr1 knock-out mutant of Arabidopsis

“…The XLGs are involved in growth, development, and defending systems [8][9][10]. The results of transcriptome analysis confirmed that GCR1 affects the response of plants to biotic and abiotic stress, hormones, secondary metabolism, and phosphate starvation [11,12]. However, the accurate roles of GCR1 remain unknown.…”