Characterization of salt stress-enhanced phosphoenolpyruvate carboxylase kinase activity in leaves of Sorghum vulgare: independence from osmotic stress, involvement of ion toxicity and significance of dark phosphorylation

Abstract

C 4 phosphoenolpyruvate carboxylase (PEP-Case: EC 4.1.1.31) is subjected to in vivo regulatory phosphorylation by a light up-regulated, calciumindependent protein kinase. Salt stress greatly enhanced phosphoenolpyruvate carboxylase-kinase (PEPCase-k) activity in leaves of Sorghum. The increase in PEPCase-k anticipated the time course of proline accumulation thereby suggesting that water stress was not involved in the kinase response to salt. Moreover, osmotic stress seemed not to be the main factor implicated, as demonstrated by the lack of effect when water availability was restricted by mannitol. In contrast, LiCl (at a concentration of 10 mM in short-term treatment of both excised leaves and whole plants) mimicked the effects of 172 mM NaCl salt-acclimation, indicating that the rise in PEPCase-k activity resulted primarily from the ionic stress. Both NaCl and LiCl treatments increased the activity of a Ca 2+ -independent, 35 kDa kinase, as demonstrated by an in-gel phosphorylation experiment. Short-term treatment of excised leaves with NaCl or LiCl partially reproduces the effects of whole plant treatments. Finally, salinization also increased PEP-Case-k activity and the phosphorylation state of PEP-Case in darkened Sorghum leaves. This fact, together with increased malate production during the dark period, suggests a shift towards mixed C 4 and crassulacean acid metabolism types of photosynthesis in response to salt stress.

Early mannitol-triggered changes in the Arabidopsis leaf (phospho)proteome reveal growth regulators

“…The only protein that was up-regulated upon mannitol treatment was PEPC. This is in agreement with previous studies where it was shown that abiotic stresses can induce PEPC gene expression in wheat, A. thaliana , and sorghum (Echevarría et al , 2001; González et al , 2003; García-Mauriño et al , 2003; Sánchez et al , 2006). Moreover, recent studies demonstrated that the maize PEPC gene was able to confer drought tolerance and increase grain yield in transgenic wheat plants (Qin et al , 2016).…”

Genome-wide Analysis of Phosphoenolpyruvate Carboxylase Gene Family and Their Response to Abiotic Stresses in Soybean

“…5; Supplementary Table S4). Previous reports also demonstrated the crucial roles of PEPC genes in various stress responses and in hormone signaling transduction278910, which motivated us to perform expression profile analyses of GmPEPC genes under various abiotic stress and hormones treatments. The results showed that Al, cold, salt or PEG stress could alter the expression level of soybean PEPC genes and soybean PEPC activity (Figs 7 and 8).…”

“…For example, studies have shown that PEPC overexpressing transgenic rice has a relatively higher photosynthetic rate under high light and temperature conditions53. In addition, abiotic stresses, such as salt and chilling injury, can induce PEPC gene expression in wheat, Arabidopsis and sorghum81054. In this study, we showed that the promoter regions of most GmPEPC genes contained 19 stress-responsive cis -regulated elements such as ABA, cold, drought, heat, salt, and wound-related elements, indicating their potential roles in soybean response to phytohormone and stresses (Fig.…”

“…Recently, accumulating evidence has confirmed that a large number of PEPC genes are induced by abiotic and biotic stresses and play important roles in regulation of plant tolerance to stress267. For example, an up-regulated PEPC expression in response to salinity or drought stress has been well documented in C 3 , C 4 and CAM plants678910. Meanwhile, overexpression of PEPC gene in transgenic plants enhanced their tolerance to drought or salt stress11, whereas knockdown of PEPC leading to increased sensitivity to osmotic stress12.…”

Changes in Soybean Global Gene Expression after Application of Lipo-Chitooligosaccharide from Bradyrhizobium japonicum under Sub-Optimal Temperature

“…In addition, PEPC plays roles in fruit ripening, regulating cellular pH, and providing malate to guard cells [69]. PEPC kinase is a Ca 2+ -independent serine/threonine kinase that phosphorylates PEPC; strikingly, PEPC kinase activity was enhanced by salt stress in Sorghum vulgare ; further analysis revealed that the induction was related to ion toxicity rather than osmotic stress [70]. Although it is uncertain which aspect of PEPC function caused its responsiveness to LCO foliar spray, any of the three indicated could be affected.…”