SDG724, the Switch of Flowering Time in Rice under Long Day Conditions Was Found

Flowering time (heading date) is one of the important agronomic traits and determines adaptation to region and season. Rice is a short-day plant. However, during the domestication of rice, the areas of cultivation are expanding to the north, even at around 45°N latitude, even northeast China becomes the one of rice main production areas. The mechanism of flowering transition under short day conditions is well studied, however, the mechanism of flowering transition under under LD conditions is much less elucidated.

Dr. Changhui Sun and Dr. Jun Fang in Dr. Chengcai Chu’s group (http://chulab.genetics.ac.cn/) from the Institute of Genetics and Developmental Biology, the Chinese Academy of Sciences carried out an extensive screening of their large rice T-DNA mutant population, and isolated a rice late flowering mutant lvp1 (long vegetative phase 1).

Map-based cloning reveals that LVP1 encodes a SET domain group protein 724(SDG724). Biochemical characterization shows SDG724 is an active histone methyltransferase (HMTase) in vivo and required for global histone lysine 36 (H3K36) deposited in vitro.

Furthermore the H3K36me2/3 levels at most detected region of RFT1, the rice florigen under long day conditions, was obviously reduced in the lvp1 mutant, but interestingly, the florigen gene Hd3a, the rice florigen under short day conditions, which situates only 11.5 kb downstream of RFT1, showed little variation on its own H3K36me2/3 level between the wild-type plant and the lvp1 mutant under both SD and LD condition.

The results indicate that H3K36me2/3 could strictly distinguish these two homologs with a clear preference to select RFT1 as its modification target in spite of their close localization on the genome.

This work not only explained the molecular mechanism involved in the adaptation of rice to the north, but also is of significance in application in improving the heading date of rice in the northeast China.

The work has been online published on Plant Cell (DOI:10.1105/tpc.112.101436). This research was supported by grants from the Chinese Academy of Sciences, Ministry of Science and Technology, Ministry of Agriculture of China, and National Natural Science Foundation of China.

AUTHOR CONTACT:

Chengcai Chu, Ph.D.

Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.

E-mail: ccchu@genetics.ac.cn