SBEIIb is responsible for the chalk2 phenotype by regulating the formation of resistant starch in indica rice

High-resistant starch rice is a valuable food for human health, especially for individuals with type 2 diabetes. It supports effective blood sugar control and provides cardiovascular and intestinal benefits. However, developing rice varieties with high resistant starch content remains a major challenge. Now, a team of researchers from China identified a mutant, chalk2, with increased chalkiness from the mutant library of indica rice ZJ100. They published their study in the Journal of Integrative Agriculture.

“The chalk2 mutants exhibited significantly higher amylose and protein contents, while total starch and lipid contents were reduced,” shares corresponding author Prof. Peisong Hu from China National Rice Research Institute. “Analysis of resistant starch in chalk2 revealed substantial increases in two resistant starch (RS) types RS2 and RS3.”

Electron microscopy revealed abnormal starch granule development in the endosperm. The chalk2 mutant also showed reduced grain length, width, and thickness, as well as a decreased seed setting rate, which ultimately led to a significant reduction in grain yield.

“Further, through physical localization, Mut-Map analysis, and transgene complementation, we found that SBEIIb was responsible for the chalk2 phynotypes, a member of the starch branching enzyme (SBE) family, specifically expressed in the endosperm,” says Hui. “The expression levels, enzyme activity, and protein abundance of SBEIIb were significantly reduced in chalk2 mutants.”

“These findings suggest that SBEIIb plays a crucial role in regulating the composition of starch and resistant starch formation in indica rice.” adds co-corresponding author Prof. Xiangjin Wei, from the same institute.

Contact Authors:

Correspondence Peisong Hu, E-mail: peisonghu@126.com; Xiangjin Wei, E-mail: weixiangjin@caas.cn

Funder:

This work was supported by by grants from the National Natural Science Foundation of China (32372099 and 32188102), the Natural Science Foundation of Zhejiang Province, China (LQ24C130007), and the Innovation Program of Chinese Academy of Agricultural Sciences (CAAS-CSCB-202402).

Conflict of Interest:

The authors declare that they have no conflict of interest.

See the Article:

Li X W et al. 2026. SBEIIb is responsible for the chalk2 phenotype by regulating the formation of resistant starch in indica rice. Journal of Integrative Agriculture, 25(7): 2688-2700.