Molecular and Biochemical Analysis of the Gelatinization Temperature Character in Rice (Oryza Sativa L.)

Summary

Through integrated molecular and biochemical investigations and by using a common mutant line in molecular mapping, our present study proved that the SSIIa gene, previously reported to be responsible for the gelatinization temperature (GT) differences between indica and japonica rice varieties, might also control the GT variations among certain indica varieties, through synthesizing different types of amylopectin molecules due to the differences of SSIIa protein amounts bound to starch granules. Our study further demonstrated, for the first time, that the amylopectin type could only account for the GT differences between varieties with different SSIIa alleles, but not among varieties carrying a common SSIIa allele. In the latter case, another gene, alk2(t), with a genetic distance of 3.93 cM from the Wx gene, was identified out to be responsible for the GT variations.

Based on the thermal properties and amylopectin chain length profile characteristics, it is postulated that the SSIIa gene has at least three different alleles, one in japonica rice and two in indica rice varieties, while the alk2(t) has at least two alleles for either low or high GT, and the rich diversity of the GT character is very probably resulting from various combinations of these gene alleles in rice.