Suppression of sucrose synthase affects auxin signaling and leaf morphology in tomato

<div><p>Metabolic enzymes have been found to play roles in plant development. Sucrose synthase (SUS) is one of the two enzyme families involved in sucrose cleavage in plants. In tomato, six SUS genes have been found. We generated transgenic tomato plants with RNAi suppression of <i>SlSUS1</i>, <i>SlSUS3</i> and <i>SlSUS4</i> genes. Independent transgenic lines with RNAi suppression of more than one <i>SUS</i> gene exhibited morphological effects on their cotyledons and leaf structure, but there were no significant effects on their carbohydrate levels, demonstrating that SUS has a developmental function, in addition to its metabolic function. Shoot apices of the transgenic lines showed elevated expression of <i>JAGGED</i> (<i>JAG</i>) and the auxin transporter <i>PIN1</i>. In a PIN1-GFP fusion reporter/SUS-RNAi hybrid, PIN1-GFP patterns were altered in developing leaves (as compared to control plants), indicating that <i>SlSUS</i> suppression alters auxin signaling. These results suggest possible roles for SUS in the regulation of plant growth and leaf morphology, in association with the auxin-signaling pathway.</p>