Abstract
Rice empty glumes, also named sterile lemmas or rudimentary lemmas according to different interpretations, are distinct from lemmas in morphology and cellular pattern. Consistently, the molecular mechanism to control the development of lemmas is different from that of empty glumes. Rice LEAFY HULL STERILE1(OsLHS1) and DROOPING LEAF(DL) regulate the cellular pattern and the number of vascular bundles of lemmas respectively, while LONG STERILE LEMMA1 (G1)/ELONGATED EMPTY GLUME (ELE) and PANICLE PHYTOMER2 (PAP2)/OsMADS34 determine identities of empty glumes. Though some progress has been made, identities of empty glumes remain unclear, and genetic interactions between lemma genes and glume genes have been rarely elucidated. In this research, a new G1/ELE mutant g1–6 was identified and the phenotype was analyzed. Similar to previously reported mutant lines of G1/ELE, empty glumes of g1–6 plants transform into lemma-like organs. Furthermore, Phenotypes of single and double mutant plants suggest that, in addition to their previously described gene-specific functions, G1/ELE and OsLHS1 play redundant roles in controlling vascular bundle number, cell volume, and cell layer number of empty glumes and lemmas. Meanwhile, expression patterns of G1/ELE in osmads1-z flowers and OsLHS1 in g1–6 flowers indicate they do not regulate each other at the level of transcription. Finally, down-regulation of the empty glume gene OsMADS34/PAP2 and ectopic expression of the lemma gene DL, in the g1–6 plants provide further evidence that empty glumes are sterile lemmas. Generally, our findings provided valuable information for better understanding functions of G1 and OsLHS1 in flower development and identities of empty glumes.
Highlights
Flower development is the basis for seed development in angiosperms
Since plants of long sterile lemma1 and elongated empty glume displayed similar phenotypes and the G1/EMPTY GLUME (ELE) gene was mapped in the same region (Yoshida et al, 2009; Hong et al, 2010), we considered if a mutation of G1/ELE occurred in our mutant plants
No obvious expression of OsMADS34/PANICLE PHYTOMER2 (PAP2) in abnormal glumes of either g1–6 or double mutant plants was detected (Figure 8D). These results suggested that G1/ELE regulate the expression of OsMADS34/PAP2 positively in empty glumes
Summary
Flower development is the basis for seed development in angiosperms. Based on analyses of flower mutants in Arabidopsis thaliana and Antirrhinum majus, the ABCDE model was proposed to interpret the molecular mechanism in control of flower development (Coen and Meyerowitz, 1991; Pelaz et al, 2000; Theissen, 2001; Theissen and Saedler, 2001; Ditta et al, 2004).Analyses of Genetic Interaction between G1 and OsLHS1Rice (Oryza sativa L.) is a model plant of monocots and one important cereal crop. Flower development is the basis for seed development in angiosperms. Based on analyses of flower mutants in Arabidopsis thaliana and Antirrhinum majus, the ABCDE model was proposed to interpret the molecular mechanism in control of flower development (Coen and Meyerowitz, 1991; Pelaz et al, 2000; Theissen, 2001; Theissen and Saedler, 2001; Ditta et al, 2004). Rice (Oryza sativa L.) is a model plant of monocots and one important cereal crop. The structural units of the rice flower are spikelets and florets. The spikelet is the primary unit of the rice inflorescence and contains a fertile floret and a pair of empty glumes ( called “sterile lemmas” or “rudimentary lemmas”), subtended by a pair of highly reduced glumes called rudimentary glumes. The floret consists of a pair of bract-like organs (lemma and palea), two lodicules (equivalent to eudicot petals), six stamens, and a carpel (Yoshida and Nagato, 2011; Lombardo and Yoshida, 2015)
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