Lateral plant organs, particularly leaves, initiate at the flanks of the shoot apical meristem (SAM) following auxin maxima signals; however, little is known about the underlying mechanisms. Here, we show that tomato leafless (lfs) mutants fail to produce cotyledons and leaves and grow a naked pin while maintaining an active SAM. A similar phenotype was observed among pin-like shoots induced by polar auxin transport inhibitors such as 2,3,5-triiodobenzoic acid (TIBA). Both types of pin-like shoots showed reduced expression of primordia markers as well as abnormal auxin distribution, as evidenced by expression of the auxin reporters pPIN1: PIN1:GFP and DR5:YFP. Upon auxin microapplication, both lfs meristems and TIBA-pin apices activated DR5:YFP expression with similar kinetics; however, only lfs plants failed to concurrently initiate leaf primordia. We found that LFS encodes the single tomato ortholog of Arabidopsis DORNRONSCHEN (DRN) and DRN-like (DRNL) genes and is transiently expressed at incipient and young primordia, overlapping with auxin response maxima. LFS is rapidly induced by auxin application, implying feed-forward activity between LFS and auxin signals. However, driving LFS at auxin response maxima sites using the DR5 promoter fails to fully rescue lfs plants, suggesting that additional, auxin-independent regulation is needed. Indeed, extended GCC-box elements upstream of LFS drove primordia-specific expression in a LFS-dependent but auxin-independent manner. We thus suggest that LFS transiently acts at the site of primordia initiation, where it provides a specific context to auxin response maxima culminating in leaf primordia initiation.
Capua, Y., Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel, Faculty of Agriculture, Hebrew University of Jerusalem, Rehovot, 76100, Israel; Eshed, Y., Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel
Recommended Citation:
Capua Y.,Eshed Y.. Coordination of auxin-triggered leaf initiation by tomato LEAFLESS[J]. Proceedings of the National Academy of Sciences of the United States of America,2017-01-01,114(12)