ZmSPL13andZmSPL29act together to promote vegetative and reproductive transition in maize

Abstract

SummaryFlowering time is a key agronomic trait determining environmental adaptation and yield potential of crops. The regulatory mechanisms of flowering in maize still remain rudimentary.In this study, we combine expressional, genetic, and molecular studies to identify two homologousSQUAMOSA PROMOTER BINDING PROTEIN‐LIKE(SPL) transcription factorsZmSPL13andZmSPL29as positive regulators of juvenile‐to‐adult vegetative transition and floral transition in maize.We show that bothZmSPL13andZmSPL29are preferentially expressed in leaf phloem, vegetative and reproductive meristem. We show that vegetative phase change and flowering time are moderately delayed in theZmspl13andZmspl29single knockout mutants and more significantly delayed in theZmspl13/29double mutants. Consistently, theZmSPL29overexpression plants display precocious vegetative phase transition and floral transition, thus early flowering. We demonstrate thatZmSPL13andZmSPL29directly upregulate the expression ofZmMIR172CandZCN8in the leaf, and ofZMM3andZMM4in the shoot apical meristem, to induce juvenile‐to‐adult vegetative transition and floral transition.These findings establish a consecutive signaling cascade of the maize aging pathway by linking the miR156‐SPL and the miR172‐Gl15 regulatory modules and provide new targets for genetic improvement of flowering time in maize cultivars.