SRA

Abscisic acid (ABA) regulates plant development and adaptation to environmental conditions. The ABA biosynthesis pathway in plants has been thoroughly elucidated; however, very few transcription factors directly regulating the expression of ABA biosynthetic genes have been identified. Here we show that the tomato (Solanum lycopersicum) zinc finger transcription factor SlZFP2, which is mainly expressed in developing fruits and axillary buds, negatively regulates ABA biosynthesis. Overexpression of SlZFP2 resulted in multiple phenotypic changes, including more branches, early flowering, delayed fruit ripening, lighter seeds and faster seed germination, whereas gene silencing by RNA interference (RNAi) caused poor fruit set and inhibited seed germination. Gene expression analysis showed that SlZFP2 represses ABA biosynthesis mainly through downregulation of the ABA biosynthetic genes SITIENS (SIT), FLACCA (FLC) and aldehyde oxidase SlAO1. SlZFP2 delays the onset of ripening through suppression of the ripening regulator COLORLESS NON-RIPENING (CNR). Using bacterial one hybrid screening and a selected amplification and binding assay we identified the (A/T)(G/C)TT repeat as the core binding sequence of SlZFP2. We further identified a large number of tomato genes containing putative SlZFP2 binding sites in their promoter regions. Chromatin immunoprecipitation and electrophoretic mobility shift assays demonstrated that SIT, FLC and SlAO1 are direct targets of SlZFP2 through binding to their promoter regions. We propose that SlZFP2 represents a novel negative regulator for fine tuning ABA biosynthesis during fruit development and provides a potentially valuable tool for dissecting the role of ABA in fruit ripening.To gain further insight on transcriptome changes regulated by SlZFP2, we sequenced a representative SlZFP2 RNAi line in LA1589 background and its nontransgenic sibling (WT) on a Miseq platform. Overall design: The RNAi line 207 showed defected fruit set and ABA biosynthesis were chosen for profiling gene expression via RNA sequencing. Its nontransgenic sibling was served as controls. Three biological replicates were conducted.