Cloning and Expression Analysis cf Two Photosynthetic Genes, PSI-H and LHCB1, Under Trehalose Feeding Conditions in Arabidipsis Seedlings

Trehalose (a-D-glucosyl-[1,1]-a-D-glucopyranoside) is involved in mechanisms that coordinate metabolism with plant growth adaptation and development. The main objective of the current work was to find out whether trehalose feeding affects the expression of two genes involved in photosynthesis: one gene coding for photosystem1 subunit H (PS1-H) and the other for the light harvesting complex B1 (LHCB1). In this study, Arabidopsis seeds were grown on one-half-strength medium supplemented with 100 mM trehalose or sorbitol (as osmotic control) for 2 weeks. Trehalose-fed seedlings showed inhibited root growth, delayed emergence of primary cotyledons and dark-rimmed cotyledons. Exogenously applied trehalose strongly induced starch accumulation in cotyledons and, concomitantly, depletion of starch in collumella cells of the root cap. Gene expression analysis of photosynthetic genes in Arabidopsis seedlings revealed that trehalose feeding repressed PS1-H and LHCB1 expression as compared to sorbitol-fed seedlings. To confirm trehalose inhibitory effect on photosynthetic gene expression, the cDNA of PS1-H and LHCB1 was used to transform Arabidopsis seedlings. Transformed lines showed higher transcript levels of PS1-H and LHCB1.Trehalose feeding also reduced expression levels of PS1-H and LHCB1 in transformed lines. These findings show that trehalose down-regulates the expression of two genes encoding typical components of the photosynthetic machinery.