Increased leaf size: different means to an end (experiment 1)

The final size of plant organs such as leaves is tightly controlled by environmental and genetic factors that must spatially and temporally coordinate cell expansion and cell cycle activity. However this regulation of organ growth is still poorly understood. The aim of this study is to gain more insight in the genetic control of leaf size in Arabidopsis by performing a comparative analysis of transgenic lines that produce larger leaves under standardized environmental conditions. To this end, we selected five genes, belonging to different functional classes, that all positively affect leaf size when over-expressed: AVP1, GRF5, JAW, BRI1 and GA20OX1. We show that the increase in leaf area in these lines depends on leaf position and growth conditions and that all five lines affect leaf size differently. However, in all cases an increase in cell number is, entirely or predominantly, responsible for the leaf size enlargement. By means of analyses of hormone levels, transcriptome and metabolome we provide deeper insight in the molecular basis of the growth phenotype for the individual lines. A comparative analysis between them indicates that enhanced organ growth is governed by different, seemingly independent pathways. The analysis of transgenic lines simultaneously over-expressing two growth-enhancing genes further supports the concept that multiple pathways independently converge on organ size control in Arabidopsis.

9

Gonzalez N, De Bodt S, Sulpice R, Jikumaru Y, Chae E, Dhondt S, Van Daele T, De Milde L, Weigel D, Kamiya Y, Stitt M, Beemster GT, Inzé D