Haplotyping and Evolutionary Studies on GBSSII Gene in Korean Rice Collection

Granules-bound starch synthase II (GBSSII), one of the isoforms of granule-bound starch synthase (GBSS), is responsible for amylose synthesis by expressing in non-storage tissues such as leaf, stem, root, and pericarp. Up to date, little is known about this gene functions and basic knowledge of heritable characteristics of this gene, GBSSII. We identified functional haplotypes and performed evolutionary analyses on the GBSSII using 374 rice accessions (320 Korean bred and 54 wild) based on the classified groups. A total of 14 haplotypes were found, and almost all haplotypes (13) were functional, carrying 19 non-synonymous SNPs in two exons (exons 1 and 2). The lowest nucleotide diversity was detected in Tropical japonica (0.00145), while the highest pi-value was in Aus (0.01081), illustrating the signal of this gene evolution. The highest Tajima's D value in Aus (1.6380) indicates GBSSII gene domestication signature under balancing selection, while the lowest Tajima's D value in Temperate japonica (-0.8243) highlights that they were under positive selection, which may be purified due to the excess of rare alleles. The highest genetic differentiation was observed between Tropical japonica and aroma (F_ST = 0.921928). In contrast, the highest interbreed level was detected in Aus-admixture (F_ST = -0.20157). The genetic relatedness between and or among the wild and cultivated subpopulations was revealed through PCA, population structure, and phylogenetic analyses.