A Putative Gene sbe3-rs for Resistant Starch Mutated from SBE3 for Starch Branching Enzyme in Rice (Oryza sativa L.)

Abstract

Foods high in resistant starch (RS) are beneficial to prevent various diseases including diabetes, colon cancers, diarrhea and chronic renal or hepatic diseases. Elevated RS in rice is important for public health since rice is a staple food for half of the world population. A japonica mutant ‘Jiangtangdao 1’ (RS = 11.67%) was crossed with an indica cultivar ‘Miyang 23’ (RS = 0.41%). The mutant sbe3-rs that explained 60.4% of RS variation was mapped between RM6611 and RM13366 on chromosome 2 (LOD = 36) using 178 F2 plants genotyped with 106 genome-wide polymorphic SSR markers. Using 656 plants from four F3∶4 families, sbe3-rs was fine mapped to a 573.3 Kb region between InDel 2 and InDel 6 using one STS, five SSRs and seven InDel markers. SBE3 which codes for starch branching enzyme was identified as a candidate gene within the putative region. Nine pairs of primers covering 22 exons were designed to sequence genomic DNA of the wild type for SBE3 and the mutant for sbe3-rs comparatively. Sequence analysis identified a missense mutation site where Leu-599 of the wild was changed to Pro-599 of the mutant in the SBE3 coding region. Because the point mutation resulted in the loss of a restriction enzyme site, sbe3-rs was not digested by a CAPS marker for SpeI site while SBE3 was. Co-segregation of the digestion pattern with RS content among 178 F2 plants further supported sbe3-rs responsible for RS in rice. As a result, the CAPS marker could be used in marker-assisted breeding to develop rice cultivars with elevated RS which is otherwise difficult to accurately assess in crops. Transgenic technology should be employed for a definitive conclusion of the sbe3-rs.

Identification of QTLs for resistant starch and total alkaloid content in brown and polished rice

“…Yet, information about RS-related genes in rice is very limited; we found two reports about RS QTLs (Mou et al, 2008;Yang et al, 2012), and none about total alkaloid-related genes. Gong et al (2013) performed a genetic analysis of the rice metabolome that provided over 2800 highly resolved metabolic QTLs for 900 metabolites.…”

“…Gong et al (2013) performed a genetic analysis of the rice metabolome that provided over 2800 highly resolved metabolic QTLs for 900 metabolites. The sbe3-rs was fine-mapped to a 573.3-kb region between InDel 2 and InDel 6 on chromosome 2, which explained 60.4% of RS variation (Yang et al, 2012). In this report, we provide evidence of a relationship between rice simple sequence repeat (SSR) markers and high RS as well as total alkaloids, which will be useful for elucidating the mechanism of functional components and utilizing favorable genes from Gongmi No.…”

“…RS content in rice was measured according to Goñi method (Goñi et al, 1996), which has been widely used for RS determination in crops (Yang et al, 2012;Shu et al, 2013). According to this method, 0.1 g rice powder was taken in 10-mL centrifuge tubes each, 4 mL (3000 U/mL) reaction liquid of pancreatic alpha-amylase was added to each tube, and the tubes were placed in a vibrator (200 times/min) in a water bath at 37°C for 16 h. Then, 4 mL 95% ethanol was added and, after vortex mixing, the tubes were subjected to centrifugation at 5000 rpm for 10 min, and the supernatant discarded.…”

“…3 from boro groups is the natural variation of rice landrace in Yunnan Province, but using radiation at 0.5 kGy, an indica mutant RS4H produces up to 8.07% resistant starch (Shu et al, 2013). Similarly, using young panicles for 0.015% of N-methylnitrosourea solution technology, a japonica mutant 'Jiangtangdao 1' produces up to 11.67% resistant starch (Yang et al, 2012). The differences between natural variation (Gongmi No.…”

“…Foods high in RS are beneficial for preventing various diseases including diabetes, colon cancer, and chronic renal or hepatic diseases. Elevated RS in rice is important for public health since rice is a staple food for half of the world's population (Yang et al, 2012). Treatment with gamma irradiation has a potential for increasing resistant starch content and reducing the digestibility of starch in common rice (Shu et al, 2013).…”