OsJAR1 is required for JA-regulated floret opening and anther dehiscence in rice

Abstract

Jasmonates are important phytohormones regulating reproductive development. We used two recessive rice Tos17 alleles of OsJAR1, osjar1-2 and osjar1-3, to study the biological function of jasmonates in rice anthesis. The florets of both osjar1 alleles stayed open during anthesis because the lodicules, which control flower opening in rice, were not withering on time. Furthermore, dehiscence of the anthers filled with viable pollen, was impaired, resulting in lower fertility. In situ hybridization and promoter GUS transgenic analysis confirmed OsJAR1 expression in these floral tissues. Flower opening induced by exogenous applied methyl jasmonate was impaired in osjar1 plants and was restored in a complementation experiment with transgenics expressing a wild type copy of OsJAR1 controlled by a rice actin promoter. Biochemical analysis showed that OsJAR1 encoded an enzyme conjugating jasmonic acid (JA) to at least Ile, Leu, Met, Phe, Trp and Val and both osjar1 alleles had substantial reduction in content of JA-Ile, JA-Leu and JA-Val in florets. We conclude that OsJAR1 is a JA-amino acid synthetase that is required for optimal flower opening and closing and anther dehiscence in rice.

Roles of jasmonate signalling in plant inflorescence and flower development

“…The C-class floral homeotic gene AGAMOUS controls lateral stamen development by directly regulating the expression of DAD1 (Figure 3b) Anthesis, an essential step in plant propagation, includes flower opening and closure, anther dehiscence and fertilization. In rice, flower opening can be induced by applied JA, and osjar1 plants had impaired anthesis [61], which is different from the normal flower development of Arabidopsis jar1. The expression of OsJAR1 is detectable in the lodicules 1-2 days prior to anthesis (Figure 3c), indicating that the timely expression of OsJAR1 in lodicules is critical for the control of flower opening time.…”

Synthesis and Functions of Jasmonates in Maize

“…In rice, JAR1 was determined to be involved in photomorphogenesis [101], floret development [102] and phytoalexin production [103]. The presence of multiple JAR1-like isoforms in maize will require utilization of double mutants for functional characterization.…”

Development of a multiple-hybrid population for genome-wide association studies: theoretical consideration and genetic mapping of flowering traits in maize

“…Peak SNPs on the short arm of chromosome 8 (bin 8.01) revealed a phosphatidylethanolamine-binding protein ( ZCN9 ) gene GRMZM2G021614 105, the homologous gene in rice LOC_Os01g02120.1 promoting the transition from vegetative to reproductive growth. The peak mapped on bin 8.05 was predicted with one candidate gene GRMZM2G091276 , a homologous gene in rice ( LOC_Os05g50890.1) OsGH3.5 coding JA-amino acid synthetase1 modulating light and JA signal in the photomorphogenesis106 and flower opening and anther dehiscence107.…”