The SEPALLATA-Like Gene OsMADS34 Is Required for Rice Inflorescence and Spikelet Development      

Abstract

Grass plants develop distinct inflorescences and spikelets that determine grain yields. However, the mechanisms underlying the specification of inflorescences and spikelets in grasses remain largely unknown. Here, we report the biological role of one SEPALLATA (SEP)-like gene, OsMADS34, in controlling the development of inflorescences and spikelets in rice (Oryza sativa). OsMADS34 encodes a MADS box protein containing a short carboxyl terminus without transcriptional activation activity in yeast cells. We demonstrate the ubiquitous expression of OsMADS34 in roots, leaves, and primordia of inflorescence and spikelet organs. Compared with the wild type, osmads34 mutants developed altered inflorescence morphology, with an increased number of primary branches and a decreased number of secondary branches. In addition, osmads34 mutants displayed a decreased spikelet number and altered spikelet morphology, with lemma/leaf-like elongated sterile lemmas. Moreover, analysis of the double mutant osmads34 osmads1 suggests that OsMADS34 specifies the identities of floral organs, including the lemma/palea, lodicules, stamens, and carpel, in combination with another rice SEP-like gene, OsMADS1. Collectively, our study suggests that the origin and diversification of OsMADS34 and OsMADS1 contribute to the origin of distinct grass inflorescences and spikelets.

RiceLHS1/OsMADS1Controls Floret Meristem Specification by Coordinated Regulation of Transcription Factors and Hormone Signaling Pathways

“…OsMADS34 transcripts are at reduced levels in the young FM. In contrast, OsMADS1 transcripts are abundant in the incipient FM and nearly undetectable in empty glumes (Prasad et al, 2001;Gao et al, 2010;Kobayashi et al, 2010Kobayashi et al, , 2012. We found 4-fold increased transcript levels for OsMADS34 in PUbi: OsMADS1-DGR; P35S:OsMADS1amiR panicles (Fig.…”

“…But members of a grassspecific subgroup in the LOFSEP clade, OsMADS1, OsMADS5, and OsMADS34, have acquired novel functions (Malcomber and Kellogg, 2005;Gao et al, 2010;Kobayashi et al, 2010). OsMADS34 regulates panicle branching and promotes spikelet meristem and empty glume fate (Gao et al, 2010;Kobayashi et al, 2010Kobayashi et al, , 2012. OsMADS1 is expressed developmentally slightly later and is restricted to the incipient FM region of the spikelet and controls its fate (Jeon et al, 2000;Prasad et al, 2005).…”

“…Of the five SEPlike rice genes, OsMADS7 and OsMADS8 are members of SEP3 clade and have retained conserved functions, as they regulate organ development in inner floret whorls (Cui et al, 2010). But members of a grassspecific subgroup in the LOFSEP clade, OsMADS1, OsMADS5, and OsMADS34, have acquired novel functions (Malcomber and Kellogg, 2005;Gao et al, 2010;Kobayashi et al, 2010). OsMADS34 regulates panicle branching and promotes spikelet meristem and empty glume fate (Gao et al, 2010;Kobayashi et al, 2010Kobayashi et al, , 2012.…”

“…OsMADS34, a rice LOFSEP member, regulates inflorescence branching and promotes spikelet meristem fate (Gao et al, 2010;Kobayashi et al, 2010Kobayashi et al, , 2012 and thus is suggested to act temporally earlier than OsMADS1. In developing panicles, spikelets, and florets, these two genes have partly exclusive and some overlapping expression patterns (Kobayashi et al, 2010).…”

“…They contribute to panicle morphology, spikelet and FM specification, floral organ differentiation, and meristem determinacy (Jeon et al, 2000;Prasad et al, 2005;Cui et al, 2010;Gao et al, 2010;Kobayashi et al, 2010). Rice LEAFY HULL STERILE (LHS1)/OsMADS1, a member of the grass subgroup of LOFSEP genes, referred to henceforth as OsMADS1, is expressed in FMs, functions during FM establishment and floret organ patterning, and contributes to meristem termination (Jeon et al, 2000;Prasad et al, 2001Prasad et al, , 2005Agrawal et al, 2005;Ohmori et al, 2009;Cui et al, 2010;Gao et al, 2010;Li et al, 2010;Wang et al, 2010). In addition to studies on mutants in rice SEP factors, their protein-protein interactions are reported from yeast two-hybrid analyses.…”