Abstract
Trehalose-6-phosphate (T6P) phosphatase (TPP), a dephosphorylating enzyme, catalyzes the dephosphorylation of T6P, generating trehalose. In Jatropha, we found six members of the TPP family. Five of them JcTPPA, JcTPPC, JcTPPD, JcTPPG, and JcTPPJ are highly expressed in female flowers or male flowers, or both, suggesting that members of the JcTPP family may participate in flower development in Jatropha. The wide expression of JcTPPJ gene in various organs implied its versatile roles and thus was chosen for unraveling its biological functions during developmental process. We constructed an overexpression vector of JcTPPJ cDNA driven by the cauliflower mosaic virus (CaMV) 35S promoter for genetic transformation. Compared with control Arabidopsis plants, 35S:JcTPPJ transgenic Arabidopsis plants presented greater sucrose contents in their inflorescences and displayed late-flowering and heterostylous phenotypes. Exogenous application of sucrose to the inflorescence buds of wild-type Arabidopsis repressed the development of the perianth and filaments, with a phenocopy of the 35S:JcTPPJ transgenic Arabidopsis. These results suggested that the significantly increased sucrose level in the inflorescence caused (or induced) by JcTTPJ overexpression, was responsible for the formation of heterostylous flower phenotype. However, 35S:JcTPPJ transgenic Jatropha displayed no obvious phenotypic changes, implying that JcTPPJ alone may not be sufficient for regulating flower development in Jatropha. Our results are helpful for understanding the function of TPPs, which may regulate flower organ development by manipulating the sucrose status in plants.
Highlights
Trehalose, a stable non-reducing α-d-glucopyranosyl α-d-glucopyranoside, is present in all organisms except vertebrates [1,2]
A total of six genes JcTPPA, JcTPPC, JcTPPD, JcTPP1, JcTPPG, and JcTPPJ that are homologous to Arabidopsis trehalose-6-phosphate phosphatase (AtTPP) genes were identified from Jatropha
Overexpressing JcTPPJ in Arabidopsis results in phenotypes similar to those of AtTPPB, AtTPPC, and AtTPPI transgenic plants; the filaments of the stamen are relatively short in 35S:JcTPPJ transgenic Arabidopsis, which implies that JcTPPJ plays a stronger role in preventing the development of male floral organs than does AtTPPB, AtTPPC, and AtTPPI as assessed by their overexpression in transgenic plants (Figure 5)
Summary
A stable non-reducing α-d-glucopyranosyl α-d-glucopyranoside, is present in all organisms except vertebrates [1,2]. Trehalose biosynthesis involves in two consecutive enzymatic reactions. Trehalose-6-phosphate (T6P) synthase (TPS) catalyzes a reaction between both uridine diphosphate glucose (UDP-Glu) and glucose-6-phosphate, which produces the intermediate product T6P. T6P phosphatase (TPP) catalyzes the dephosphorylation of T6P to generate trehalose [1]. Trehalase (TRE) catalyzes the hydrolysis of trehalose into two units of glucose [1,6]. Arabidopsis thaliana has eleven TPS genes (AtTPS1-11, class I and II trehalose biosynthesis genes), ten TPP genes (TPPA-J, class III trehalose biosynthesis genes) and one TRE gene [7,8]. The TPS and TPP gene families are present in other flowering plants [9,10,11,12]
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