OsRRMh, a Spen‐Like Gene, Plays an Important Role During the Vegetative to Reproductive Transition in Rice

Abstract

OsRRMh, a homologue of OsRRM, encodes a Spen‐like protein, and is composed of two N‐terminal RNA recognition motifs (RRM) and one C‐terminal Spen paralogue and an orthologue C‐terminal domain (SPOC). The gene has been found to be constitutively expressed in the root, stem, leaf, spikelet, and immature seed, and alternative splicing patterns were confirmed in different tissues, which may indicate diverse functions for OsRRMh. The OsRRMh dsRNAi lines exhibited late‐flowering and a larger panicle phenotype. When full‐length OsRRMh and/or its SPOC domain were overexpressed, the fertility rate and number of spikelets per panicle were both markedly reduced. Also, overexpression of OsRRMh in the Arabidopsis fpa mutant did not restore the normal flowering time, and it delayed flowering in Col plants. Therefore, we propose that OsRRMh may confer one of its functions in the vegetative‐to‐reproductive transition in rice (Oryza sativa L. subsp. japonica cv. Zhonghua No. 11 (ZH11)).

Expression analysis of the Arabidopsis thaliana AtSpen2 gene, and its relationship with other plant genes encoding Spen proteins

“…The OsRRMh gene is expressed in the roots, stem, leaves, and immature seeds, and it is alternatively spliced in different tissues, suggesting its involvement in several biological functions. When this gene was knocked down by dsRNAi, the flowering was retarded and the panicle phenotype was larger, which was in agreement with the down-regulation of two flowering-related genes of rice: RFT1 and Hd3a ( Liu and Cai, 2013 ).…”

“…This hypothesis is supported by the results of the phenotypic analysis of A. thaliana AtSpen2 KO mutants and transgenic OE lines, as flowering time was not modified compared to WT plants. In contrast, inactivation of fpa in A. thaliana ( Schomburg et al , 2001 ) and its orthologous gene OsRRMh in rice ( Liu and Cai, 2013 ) produced a delay in flowering, hence demonstrating that the function of both proteins in flowering control has been preserved through the evolution of angiosperms. It can be hypothesized that the ancestral gene encoding a Spen protein in plants was duplicated before separation of dicots and monocots and that a process of functional divergence took place throughout the subsequent evolution of those plant lineages.…”

Genome-Wide Association Study for Plant Height and Grain Yield in Rice under Contrasting Moisture Regimes

“…OsRRMh (LOC_Os09g34070) was 157 kb away from the significant association signal (sf0920270490) (Figure 2B, Table 4) and has been reported to regulate fertility rate and number of spikelet per panicle (Liu and Cai, 2013). …”

“…OsRRMh plays an important role during the transition from vegetable to reproductive phase in rice. Compared to the wild-type, the OsRRMh RNAi lines exhibit enlarged panicles while over-expression of OsRRMh lines lead to lower fertility rates and less number of spikelets per panicle (Liu and Cai, 2013). …”

Histone 2B monoubiquitination complex integrates transcript elongation with RNA processing at circadian clock and flowering regulators

“…In the Arabidopsis genome, only three Spen proteins were retrieved that combined SPOC with one or more RRM motifs: (i) the SPEN3 protein studied in this work with one RRM, (ii) the SPEN2 (AT4G12640) protein with two RRMs with an unknown function [because the knockout and overexpressing lines had no apparent phenotype (29)], and (iii) the flowering-time regulator FPA with three RRMs that controls alternative splicing and polyadenylation of antisense transcripts of the floral repressor FLC (30). The role in floweringtime regulation has also been suggested in rice (Oryza sativa) for the Spen protein encoded by the OsRRMh gene with two RRM motifs, as indicated by the flowering-time delay in the knockdown line (31). Spen proteins with one, two, or three RRM domains occur throughout eudicots.…”