Grasses display highly diversified inflorescence architectures that differ in the arrangement of spikelets and flowers and determine cereal yields. However, the molecular basis underlying grass inflorescence morphogenesis remains largely unknown. Here we investigate the role of a functionally diversified SEPALLATA MADS-box transcription factor, OsMADS34, in regulating rice(Oryza sativa L.)inflorescence and spikelet development. Microarray analysis showed that, at the very early stages of inflorescence formation, dysfunction of OsMADS34 caused altered expression of 379 genes that are associated with protein modification and degradation, transcriptional regulation,signaling and metabolism activity. Genetic analysis revealed that OsMADS34 controls different aspects of inflorescence structure, branching and meristem activity synergistically with LAX PANICLE1(LAX1) and FLORAL ORGAN NUMBER4(FON4), as evidenced by the enhanced phenotypes of osmads34 lax1 and osmads34 fon4 compared with the single mutants. Additionally, double mutant between osmads34 and the sterile lemma defective mutant elongated empty glume(ele) displayed an enhanced phenotype, that is,longer and wider sterile lemmas that were converted into lemma/palea-like organs, suggesting that ELE and OsMADS34 synergistically control the sterile lemma development. OsMADS34 may act together with OsMADS15 in controlling sterile lemma development. Collectively, these findings provide insights into the regulatory function of OsMADS34 in rice inflorescence and spikelet development.
Rice is one of the most important crops as it supports over25%of total caloric intake for humans(Kusano et al.,2015).The world population reached 7.3 billion in 2015 and is projected to reach 8.5 billion in 2030(Word Population Prospects:2015 Revision).To meet the food demands for the everincreasing population with limited arable land,scarce
Anther cuticle and pollen exine act as protective envelopes for the male gametophyte or pollen grain, but the mechanism underlying the synthesis of these lipidic polymers remains unclear. Previously, a tapetum‐expressed CYP703A3, a putative cytochrome P450 fatty acid hydroxylase, was shown to be essential for male fertility in rice(Oryza sativa L.). However,the biochemical and biological roles of CYP703A3 has not been characterized. Here, we observed that cyp703a3‐2 caused by one base insertion in CYP703A3 displays defective pollen exine and anther epicuticular layer, which differs from Arabidopsis cyp703a2 in which only defective pollen exine occurs. Consistently, chemical composition assay showed that levels of cutin monomers and wax components were dramatically reduced in cyp703a3‐2 anthers. Unlike the wide range of substrates of Arabidopsis CYP703A2, CYP703A3 functions as an in‐chain hydroxylase only for a specific substrate, lauric acid, preferably generating 7‐hydroxylated lauric acid. Moreover, chromatin immunoprecipitation and expression analyses revealed that the expression of CYP703A3 is directly regulated by Tapetum Degeneration Retardation, a known regulator of tapetum PCD and pollen exine formation. Collectively, our results suggest that CYP703A3 represents a conserved and diversified biochemical pathway for in‐chain hydroxylation of lauric acid required for the development of male organ in higher plants.
