AUTHOR=Lu Huan , Dai Zhengyan , Li Ling , Wang Jiang , Miao Xuexia , Shi Zhenying 

TITLE=OsRAMOSA2 Shapes Panicle Architecture through Regulating Pedicel Length

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01538

DOI=10.3389/fpls.2017.01538

ISSN=1664-462X

ABSTRACT=<p>The panicle architecture of rice is an important characteristic that influences reproductive success and yield. It is largely determined by the number and length of the primary and secondary branches. The number of panicle branches is defined by the inflorescence meristem state between determinacy and indeterminacy; for example, the maize <italic>ramosa2</italic> (<italic>ra2</italic>) mutant has more branches in its tassel through loss of spikelet determinacy. Some genes and factors influencing the number of primary and secondary branches have been studied, but little is known about the molecular mechanism underlying pedicel development, which also influences panicle architecture. We report here that rice <italic>OsRAMOSA2</italic> (<italic>OsRA2</italic>) gene modifies panicle architecture through regulating pedicel length. Ectopic expression of <italic>OsRA2</italic> resulted in a shortened pedicel while inhibition of <italic>OsRA2</italic> through RNA interference produced elongated pedicel. In addition, <italic>OsRA2</italic> influenced seed morphology. The OsRA2 protein localized to the nucleus and showed transcriptional activation in yeast; in accordance with its function in pedicel development, <italic>OsRA2</italic> mRNA was enriched in the anlagen of axillary meristems, such as primary and secondary branch meristems and the spikelet meristems of young panicles. This indicates a conserved role of <italic>OsRA2</italic> for shaping the initial steps of inflorescence architecture. Genetic analysis revealed that <italic>OsRA2</italic> may control panicle architecture using the same pathway as that of the axillary meristem gene <italic>LAX1</italic> (<italic>LAX PANICLE1</italic>). Moreover, <italic>OsRA2</italic> acted downstream of <italic>RCN2</italic> in regulating pedicel and branch lengths, but upstream of <italic>RCN2</italic> for control of the number of secondary branches, indicating that branch number and length development in the panicle were respectively regulated using parallel pathway. Functional conservation between <italic>OsRA2</italic> and <italic>AtLOB</italic>, and the conservation and diversification of <italic>RA2</italic> in maize and rice are also discussed.</p>