The tomato SlIAA15 is involved in trichome formation and axillary shoot development

Abstract

• The Aux/IAA genes encode a large family of short-lived proteins known to regulate auxin signalling in plants. Functional characterization of SlIAA15, a member of the tomato (Solanum lycopersicum) Aux/IAA family, shows that the encoded protein acts as a strong repressor of auxin-dependent transcription. The physiological significance of SlIAA15 was addressed by a reverse genetics approach, revealing that SlIAA15 plays multiple roles in plant developmental processes. • The SlIAA15 down-regulated lines display lower trichome number, reduced apical dominance with associated modified pattern of axillary shoot development, increased lateral root formation and decreased fruit set. Moreover, the leaves of SlIAA15-inhibited plants are dark green and thick, with larger pavement cells, longer palisade cells and larger intercellular space of spongy mesophyll cells. • The SlIAA15-suppressed plants exhibit a strong reduction in type I, V and VI trichome formation, suggesting that auxin-dependent transcriptional regulation is required for trichome initiation. Concomitant with reduced trichome formation, the expression of some R2R3 MYB genes, putatively involved in the control of trichome differentiation, is altered. • These phenotypes uncover novel and specialized roles for Aux/IAAs in plant developmental processes, clearly indicating that members of the Aux/IAA gene family in tomato perform both overlapping and specific functions. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.