第1217回生物科学セミナー

Specification of differential growth domains in the tomato leaf margin

Prof. Naomi Ori(Hebrew University, Israel)

2018年05月07日(Mon)    13:00‐14:45  理学部2号館 講堂   

In compound leaves, auxin promotes localized blade outgrowth domains, separated by intercalary domains in which the Aux/IAA protein ENTIRE (E) inhibits auxin response and blade outgrowth. The mechanism underlying the specification of differential growth domains by auxin and its contribution to leaf-shape diversity is not clear. We have identified the tomato (solanum lycopersicum) ortholog of Arabidopsis MONOPTEROS (SlMP)/AUXIN RESPONSE FACTOR 5 and Gibberellin (GA) as coordinated growth activators acting downstream of auxin. Loss of SlMP compromises the formation of leaves, leaflets and flower organs, and substantially suppresses the ectopic blade outgrowth seen in entire/sliaa9 (e) mutants or following external auxin application. SlMP and additional related ARF genes act quantitatively to fine-tune leaf shape. Expression of several GA biosynthesis genes is elevated in e leaf-primordia, and reducing GA biosynthesis suppresses e- and auxin-mediated ectopic blade outgrowth. Our findings suggest that leaf-shape quantitatively responds to the extent of blade-outgrowth at the leaf margin. No growth or continuous growth lead to a simple leaf shape, while differential growth results in the formation of distinct, separate leaflets.