Interaction of starch branching enzyme 3 and granule-bound starch synthase 1 alleles increases amylose content and alters physico-chemical properties in japonica rice (Oryza sativa L.)

Authors: SHIM, KYU-CHAN - Chungnam National University; ADEVA, CHERYL - Chungnam National University; KANG, JU-WON - Rural Development Administration - Korea; LUONG, NGOC HA - Chungnam National University; LEE, HYUN-SOOK - Rural Development Administration - Korea; CHO, JUN-HYEON - Rural Development Administration - Korea; KIM, HYUNJUNG - Lg Chem; Tai, Thomas; AHN, SANG-NAG - Chungnam National University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2022
Publication Date: 8/5/2022
Citation: Shim, K., Adeva, C., Kang, J., Luong, N., Lee, H., Cho, J., Kim, H., Tai, T., Ahn, S. 2022. Interaction of starch branching enzyme 3 and granule-bound starch synthase 1 alleles increases amylose content and alters physico-chemical properties in japonica rice (Oryza sativa L.). Frontiers in Plant Science. 13. Article 968795. https://doi.org/10.3389/fpls.2022.968795.
DOI: https://doi.org/10.3389/fpls.2022.968795

Interpretive Summary: Most rice is used for direct human consumption in the form of milled grains. As such, starch, which is the primary constituent of rice grains, is of paramount importance to the quality, utility, and value of the rice crop. In this study, the interaction of two genes that greatly influence the two major components of starch, amylopectin (starch branching enzyme 3, SBE3) and amylose (granule-bound starch synthase 1, GBSS1), was examined by determining the effects of various combinations of alleles for each gene in very similar genetic backgrounds (i.e., near-isogenic lines or NILs). Comparison of starch-related traits of these NILs revealed that SBE3 and GBSS1 interact in the regulation of apparent amylose content and resistant starch, a form of starch that is resistant to digestion and is therefore considered to have health benefits regarding diabetes. The combination of different alleles at SBE3 and GBSS1 also influenced the expression of other starch synthesis-related genes, likely leading to differences observed in seed morphology and other physico-chemical traits of the different NILs. The alleles and allele combinations may be useful in the breeding of varieties for resistant starch or industrial starch uses.

Technical Abstract: Four near-isogenic lines (NILs) with different allele combinations of the starch branching enzyme 3 (SBE3) and granule-bound starch synthase 1 (GBSS1) were developed by crossing the japonica rice varieties ‘Dodamssal’ and ‘Hwayeong’. The associations between sequence variations in SBE3 and GBSS1, and starch-related traits were investigated. These sequence variations led to changes in seed morphology, starch structure, starch crystallinity, amylopectin chain length distribution, digestibility, apparent amylose content (AAC), and resistant starch content (RS). SBE3 and GBSS1 showed genetic interaction in regulating AAC and RS. Gene expression profiling of panicle tissues revealed significant differences in expression levels of GBSS1, SBE3, and other starch-related genes among the four NILs, indicating that variations in GBSS1 and SBE3 changed the expression level of starch-related genes. These changes may contribute to the differences observed in AAC, RS, and physico-chemical characteristics of the rice starch from the NILS.