Recently, the rice molecular design technology and application innovation team of the Institute of Crop Sciences, Chinese Academy of Agricultural Sciences found that the protein DLT forms a protein complex with the homeobox protein osh15, targets and regulates the OsBRI1 gene, and controls the molecular mechanism of differential elongation of different stem nodes of rice by coordinating the content and signal of brassinosterol through differential expression. On July 5, relevant research results were published online in the plant cell.
According to researcher Tong Hongning, the rice stem is usually composed of 5-7 visible internodes of different lengths, which determines the plant height, ear development and lodging resistance of rice, and affects the field performance and actual yield of crops. The plant hormone brassinosterol (BR) regulates important agronomic traits such as leaf angle, plant height and grain size of rice and other crops. In rice, typical brassinosterol deficient mutants usually show a dwarfing pattern with shortened differences between different internodes. For example, the different alleles of the OsBRI1 mutant D61 of the br receptor gene show DM type dwarfing with specific shortening of the proportion of the second stem node, or D6 type dwarfing with specific shortening of the lower stem node except the uppermost node, according to the severity. This phenomenon suggests that brassinosterol plays an important role in regulating the tissue pattern of different stem nodes in rice, but how to achieve this process is unclear.
In this study, the brassinosterol signal deficient mutant DLT identified by the team in the early stage was used for large-scale mutagenesis. About 25000 mutants were screened for internode traits, and two D6 dwarf mutants were isolated. It was found that both mutants carried alleles of the D6 dwarf founder gene osh15. Experimental analysis shows that DLT and osh15 have synergistic, epistatic and additive genetic effects in different tissues. The two proteins jointly regulate the expression of a large number of genes, and the number and amplitude of regulation are different in different tissues. On the other hand, molecular experiments showed that osh15 could form a complex with DLT, and osh15 and DLT had opposite expression patterns in the uppermost and lower stem nodes. At the same time, DLT promoted the direct activation effect of osh15 on OsBRI1 in a dose-dependent manner. It is worth noting that BR content showed an opposite trend in young panicles and stem nodes of the mutant, further indicating that the feedback regulation between br signal and Br synthesis is also different in different tissues. This study revealed the important role of Br in coordinating the elongation of different stem nodes, and provided a reference for the customized molecular design of different stem node lengths in rice. This work was highly praised by the journal. An article written at the same time commented that”the new br regulatory genes identified in this work can not only specifically reduce the length of some stem nodes of rice, but also promote the grain size, so as to optimize the plant type and grain type of crops at the same time. Following the first green revolution promoted by using gibberellin related genes to improve plant height, Br related genes are expected to become an important breakthrough to promote the next generation of green revolution.”
Niu Mei, an assistant researcher of the Institute of Biological Sciences, and Wang Hongru, a graduate student of the Institute of genetic development of the Chinese Academy of Sciences, are the co first authors of the paper, and researcher Tong Hongning is the corresponding author. The research was supported by the National Natural Science Foundation of China, Hainan Yazhou Bay seed laboratory and the innovation project and basic scientific research business fees of the Chinese Academy of Agricultural Sciences.
DLT and osh15 fine regulate BR signaling and metabolism to coordinate the differential elongation of different stem nodes in rice