Disruption of OsARF19 is Critical for Floral Organ Development and Plant Architecture in Rice (Oryza sativa L.)

Abstract

Floral organ development is fundamentally important to plant reproduction and seed quality, yet its underlying regulatory mechanisms are still largely unknown, especially in crop plants. In this study, we characterized rice null mutant osarf19, which was isolated from a T-DNA insertion pool. The mutant displayed three types of abnormal florets: an enlarged and degenerated palea, and an additional lemma. It also showed enlarged plant architecture, including elongated basal internodes and leaves. Cellular morphology and quantitative real-time PCR (qRT-PCR) analyses showed that cell elongation caused the enlarged organs. Transgenic RNA interference (RNAi) lines of OsARF19 had similar phenotypes to the osarf19 mutant, confirming the role of OsARF19 in floral and vegetative organ development. OsARF19 is expressed in various tissues, especially young panicles and basal internodes, which are elongated. OsARF19 was induced by IAA (indole-3-acetic acid) treatment and functioned in the nucleus. By qRT-PCR analysis, we found that disruption of OsARF19 increases expression levels of OsYUCCA and OsPIN family members, while reducing OsGHs transcription activity. The high auxin performance greatly upregulated two floral organ regulators, OsMADS29 and OsMADS22, possibly responsible for palea abnormalities in osarf19. Our data provide new knowledge on the mechanisms of floral organ development, as well as possibilities in breeding for ideal plant architecture.