OsSIZ2 regulates nitrogen homeostasis and some of the reproductive traits in rice.

Small ubiquitin-related modifier (SUMO) is a post-translational modification of proteins that has important roles in plant growth and development as well as nutrition study. OsSIZ1, a SUMO E3 ligase in rice (Oryza sativa), exerts regulatory influence on nitrogen (N) homeostasis. Here, we investigated the biological function of OsSIZ2, a paralog of OsSIZ1, in the responses to nitrogen, anther dehiscence, and seed length using a reverse genetics approach. The expression of OsSIZ2 was increased during N deficiency. Under -N condition, total N concentration in the root of OsSIZ2-Ri plants and ossiz2 was significantly increased compared with wild type. Further, 15 N-labelled uptake assay revealed the role of OsSIZ2 in acquisition and mobilization of N. Moreover, qRT-PCR analyses revealed that several genes involved in the maintenance of N homeostasis were altered in OsSIZ2 mutants. In addition, ossiz2 indicated obvious defects in anther dehiscence, pollen fertility, and seed set percentage. Interestingly, however, the seed length was longer in the mutant compared with wild type. Overall, these results suggest pivotal roles of OsSIZ2 in regulating homeostasis of N and different agronomic traits including anther and seed development.