The maize plastidic thioredoxin F-type gene ZmTrxF increases starch accumulation in transgenic Arabidopsis

Abstract

The plastidic thioredoxin F-type (TrxF) protein plays an important role in plant carbohydrate metabolism and starch biosynthesis. In this work, a TrxF gene from maize, named ZmTrxF, was isolated and transformed into Arabidopsis. Constitutive expression of ZmTrxF significantly increased starch accumulation in transgenic plants. Real-time quantitative PCR (qRT-PCR) analyses showed that the transcript levels of starch biosynthetic genes, including those encoding sucrose synthase (AtSUS), phosphoglucomutase (AtPGM), ADP-glucose pyrophosphorylase (AtAGPase-S1, AtAGPase-S2, AtAGPase-L1 and AtAGPase-L2), granule-bound starch synthase (AtGBSS I and AtGBSS II), soluble starch synthase (AtSSS I, AtSSS II, AtSSS III and AtSSS IV) and starch branching enzyme (AtSBE I and AtSBE II), were increased in transgenic plants. In contrast, there was no signifcant difference in the expression levels of α-amylase (AtAMY3) and β-amylase (AtBAM1, AtBAM3 and AtBAM4) genes. Meanwhile, the activity of the major enzymes such as AGPase, GBSS, SSS and SBE involved in starch biosynthesis was higher in transgenic plants compared to that in the wild-type (WT). Furthermore, soluble sugar content was also increased in transgenic plants. All these results suggest that ZmTrxF could be used as a candidate gene for developing high starch-accumulating plants as alternative energy crops.