Coordination of auxin-triggered leaf initiation by tomato LEAFLESS.
Proc Natl Acad Sci U S A, 2017/03/21;114(12):3246-3251.
Affiliations
PMID: 28270611DOI: 10.1073/pnas.1617146114
Impact factor: 12.779
Abstract
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.
Keywords: DRN/DRNL; SAM; TIBA pins; extended GCC-box; lateral organ formation
MeSH terms
Arabidopsis; Gene Expression Regulation, Plant; Genes, Plant; Genetic Association Studies; Indoleacetic Acids; Lycopersicon esculentum; Mutation; Phenotype; Phylogeny; Plant Leaves; Promoter Regions, Genetic; Response Elements; Signal Transduction
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