The activities of PEP carboxylase and the C4 acid decarboxylases are little changed by drought stress in three C4 grasses of different subtypes

Abstract

The C4 photosynthetic pathway involves the assimilation of CO2 by phosphoenolpyruvate carboxylase (PEPC) and the subsequent decarboxylation of C4 acids. The enzymes of the CO2 concentrating mechanism could be affected under water deficit and limit C4 photosynthesis. Three different C4 grasses were submitted to gradually induced drought stress conditions: Paspalum dilatatum (NADP-malic enzyme, NADP-ME), Cynodon dactylon (NAD-malic enzyme, NAD-ME) and Zoysia japonica (PEP carboxykinase, PEPCK). Moderate leaf dehydration affected the activity and regulation of PEPC in a similar manner in the three grasses but had species-specific effects on the C4 acid decarboxylases, NADP-ME, NAD-ME and PEPCK, although changes in the C4 enzyme activities were small. In all three species, the PEPC phosphorylation state, judged by the inhibitory effect of L-malate on PEPC activity, increased with water deficit and could promote increased assimilation of CO2 by the enzyme under stress conditions. Appreciable activity of PEPCK was observed in all three species suggesting that this enzyme may act as a supplementary decarboxylase to NADP-ME and NAD-ME in addition to its role in other metabolic pathways.

Photosynthesis of C3, C3–C4, and C4 grasses at glacial CO2

“…Significant PEP-CK activity in C 4 grasses and eudicots of the NADP-ME and NAD-ME subtypes has been previously reported (Walker et al , 1997; Wingler et al , 1999; Carmo-Silva et al , 2008; Muhaidat and McKown, 2013). These findings challenge the classical view of the C 4 subtypes, where a single decarboxylase dominates (Hatch, 1987; Furbank, 2011).…”

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).…”

“…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.…”

Analysis of Natural Variation in Bermudagrass (Cynodon dactylon) Reveals Physiological Responses Underlying Drought Tolerance

“…As a warm-season perennial grass, bermudagrass is widely used as turfgrass on sport fields, golf courses and home lawns. Drought stress is a world-wide problem, and different grass species may develop different strategies to tolerate, escape, or avoid drought stress condition [4], [7], [8], [9], [10].…”