Expressional characterization of two class I trehalose-6-phosphate synthase genes in Hevea brasiliensis (para rubber tree) suggests a role in rubber production

In plants, trehalose-6-phosphate (Tre6P) synthesized by the Tre6P synthase (TPS) acts as a signal metabolite in regulating sucrose metabolism in relation to plant growth and development. The Hevea genome predicts a total of 14 TPS genes, and two class I TPS members, HbTPS1 and 2, were explored here for their expressions under various hormone and abiotic stress treatments. HbTPS1 and 2 expressions in latex, cytoplasm of rubber-producing laticifers, were markedly affected by the treatments of ethephon (2-chloroethylphosphonic acid, an ethylene releaser), 2,4-dichlorophenoxyacetic acid, jasmonic acid and salicylic acid although in a distinct manner. HbTPS1 and 2 expressions were significantly up-regulated in a similar manner by cold (5 °C) and heat (40 °C) as examined in Hevea seedling leaves and roots, and by wounding in latex. In comparison, the drought treatment (20% PEG) posed a different effect on HbTPS1 and 2 expressions in Hevea seedlings. For example, in roots, HbTPS1 transcripts accumulated with the treatment, whereas those of HbTPS2 decreased for the first 24 h. Various hormone- and stress-responsive elements could be in silico predicted in HbTPS1 and 2 promoters, and a universal expression was observed for the HbTPS1::GUS activity in all growth stages of transgenic Arabidopsis. These results, coupled with the fact of rubber biosynthesis as a defense response using sucrose as the precursor molecule, propose a potential role of TPS genes in regulating rubber production.