DH2 regulates the development of lateral organs in rice

In most of crops, the development of lateral organs such as leaves and floral organs play important roles in architecture of plant and grain, and then determine the yield. Establishment of polarityin these lateral organs is one of the most critical events for their morphogenesis. However, the molecular mechanisms about this in rice is still not clear enough. Here, we isolated two allelic mutants named degenerated hull 2-1, -2 ( dh2-1, -2 ) in rice, exhibiting abaxially rolled leaves and rod-shaped lemmas. DH2 encoded the relatively conservative ARGONAUT 7 (AGO7) protein in plants, and expressed in the lateral organs including leaf and floral organs. When the knock-out of DH2 gene resulted in the same defects with the two allelic mutants, the over-expression lines of DH2 showed adaxially rolled leaves. Next, it was proved that DH2 was involved in the synthesis of tasiR-ARFs , the expression level of which was decreased sharply in lateral organs of dh2 mutants. And then it was found that the expression of OsARF2, OsARF3, OsARF14, and OsARF15 , the potential targets of tasiR-ARFs, was increased in lateral organs of dh2 mutants. However, it was not as expected that results of in situ hybridization showed the four ARF genes were not expressed in WT lemma, whereas they were all ectopically expressed in rod-shaped lemma in dh2 mutants. Meanwhile tasiR-ARFs was expressed in the whole lemma but not abaxial side.That means there was not a opposite expression of tasiR-ARFs and ARFs in adaxial–abaxial of lemma. Therefore, according our data, we think that the pathway of OsAGO7—tasiR-ARFs in rice was more likely involved in the whole development of lemma but not only abaxial side by restricting ectopical expression of OsARFs in the whole lemma, which was different with that in lateral organs of Arabidopsis.