AUTHOR=Chandran Viswanathan , Wang He , Gao Feng , Cao Xiao-Long , Chen Yun-Ping , Li Guo-Bang , Zhu Yong , Yang Xue-Mei , Zhang Ling-Li , Zhao Zhi-Xue , Zhao Jing-Hao , Wang Ying-Ge , Li Shuangcheng , Fan Jing , Li Yan , Zhao Ji-Qun , Li Shao-Qing , Wang Wen-Ming 

TITLE=miR396-OsGRFs Module Balances Growth and Rice Blast Disease-Resistance

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.01999

DOI=10.3389/fpls.2018.01999

ISSN=1664-462X

ABSTRACT=<p>Fitness cost is a common phenomenon in rice blast disease-resistance breeding. MiR396 is a highly conserved microRNA (miRNA) family targeting <italic>Growth Regulating Factor</italic> (<italic>OsGRF</italic>) genes. Mutation at the target site of miR396 in certain <italic>OsGRF</italic> gene or blocking miR396 expression leads to increased grain yield. Here we demonstrated that fitness cost can be trade-off in miR396-<italic>OsGRF</italic>s module via balancing growth and immunity against the blast fungus. The accumulation of miR396 isoforms was significantly increased in a susceptible accession, but fluctuated in a resistant accession upon infection of <italic>Magnaporthe oryzae</italic>. The transgenic lines over-expressing different miR396 isoforms were highly susceptible to <italic>M. oryzae</italic>. In contrast, overexpressing target mimicry of miR396 to block its function led to enhanced resistance to <italic>M. oryzae</italic> in addition to improved yield traits. Moreover, transgenic plants overexpressing <italic>OsGRF6</italic>, <italic>OsGRF7</italic>, <italic>OsGRF8</italic>, and <italic>OsGRF9</italic> exhibited enhanced resistance to <italic>M. oryzae</italic>, but showed different alteration of growth. While overexpression of <italic>OsGRF7</italic> led to defects in growth, overexpression of <italic>OsGRF6</italic>, <italic>OsGRF8</italic>, and <italic>OsGRF9</italic> resulted in better or no significant change of yield traits. Collectively, our results indicate that miR396 negatively regulates rice blast disease- resistance via suppressing multiple <italic>OsGRF</italic>s, which in turn differentially control growth and yield. Therefore, miR396-<italic>OsGRFs</italic> could be a potential module to demolish fitness cost in rice blast disease-resistance breeding.</p>