Analysis of trehalose-6-phosphate control over carbon allocation and growth in plants

Abstract

Trehalose is the non-reducing alpha-alpha-1, 1-linked glucose disaccharide. The biosynthesic precursor of trehalose, trehalose-6-phosphate (T6P), is essential for plant development, growth, carbon utilization and alters photosynthetic capacity but its mode of action is not underestood. This thesis describes a genetic approach to dissecting the pleiotropic effects of T6P in the model plant Arabidopsis thaliana. Trehalose supplied to the growth medium of Arabidopsis seedlings causes T6P accumulation that inhibits growth and allocation of carbon to the root and shoot apices. 19 trehalose resistant (trr) mutant that are resistant to 100 mM trehalose are identified from the Leclere and Bartle mutant collection. These mutants contain a T-DNA expressing randomly cloned cDNAs. The trr phenotype segregated as a dominant trait in 13 of the 19 trr mutants with over-expression of PS-I, GR-RBP2, TRR14 and repression of LHCB1 causing trehalose resistance. Mutatant analysis confirms that T6P control over starch and growth uses two separate pathways . TRR14 suppresses both the massive accumulation of starch in the cotyledons and the growth inhiition due to T6P accumulation on 100 mM trehalose. A model of interactions surrounding T6P is thus presented with TRR14 affecting immediate targets of T6P that are in common to both starch and growth control and with GR-RBP2 and LHCB1 affecting remote targets of T6P in pathway controlling growth.