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Possible involvement of phosphoenolpyruvate carboxylase and NAD-malic enzyme in response to drought stress. A case study: a succulent nature of the C4-NAD-ME type desert plant, Salsola lanata (Chenopodiaceae)
Considered that the coordination between the primary carboxylating enzyme phosphoenolpyruvate carboxylase (PEPC) and the further decarboxylaing enzymes is crucial to make the efficiency of the CO2-concentrating mechanism in C4 plants, more types of C4 plants are needed to understand their adaptation mechanisms fully. In this study, we investigated the effect of drought on carboxylating enzyme PEPC, and the further decarboxylating NAD-malic enzyme (NAD-ME) of Salsola lanata Pall. (Chenopodiaceae), an annual succulent C4-NAD-ME subtype desert plant, concerning enzyme activity, transcriptional level by real-time quantitative PCR and translational level – immunochemically, and compare S. lanata with other forms of studied plants under drought stress. The results showed that only severe stress limited PEPC enzyme activity (at pH 8.0) of S. lanata significantly. Considered that PEPC enzyme activity (at pH 8.0) was not significantly affected by phosphorylation both in control and stressed plants, the significant decrease of PEPC enzyme activity (at pH 8.0) of S. lanata under severe stress may be more related with decreased PEPC mRNA. More phosphorylated status of PEPC enzyme in plants under moderate stress in comparison with other treatments, which was supported by the ratio of PEPC enzyme activity at pH 7.3/8.0, PEPC enzyme inhibition by L-malate and the 50% inhibiting concentration of L-malate. The NAD-ME activity was decreased significantly under moderate and severe stress in comparison with control ones, coinciding with the change of leaf water content other than the amount of α-NAD-ME mRNA and protein. Leaf dehydration may cause the decrease of NAD-ME activity obviously under water stress. Compared with other C4 plants, the activities of PEPC and NAD-ME of S. lanata under drought stress showed distinct features.
FP16430 Accepted 12 August 2017
© CSIRO 2017