一个水稻丙氨酸转氨酶新等位基因突变体的鉴定和籽粒特性

Identification and kernel properties of a new allelic mutant of alanine aminotransferase in rice

从60Co辐射诱变的Kitaake突变体库中筛选到一份心白胚乳突变体M30,其糙米的粒宽、粒厚和粒重显著降低;米粉中的总淀粉含量显著降低,但贮藏蛋白含量显著升高。与野生型相比,突变体淀粉的直链淀粉组分和热浆黏度、崩解值、最终黏度及糊化温度显著降低。突变体胚乳中央复粒淀粉明显减少,含有大量小的单粒淀粉,且淀粉粒之间间隙较大。利用M30/Dular的F2群体中不透明极端个体将突变基因定位到第10染色体的64.9 kb区间,该区间含有7个开放阅读框(ORF),其中ORF4编码水稻丙氨酸转氨酶1 (OsAlaAT1)。测序发现定位区间内突变体只有OsAlaAT1基因序列上缺失872 bp。在突变位点设计的InDel标记可与定位群体中的不透明极端个体发生共分离,而22个常规水稻品种中不含该突变位点。荧光定量PCR技术检测发育胚乳中淀粉合成相关基因的表达,结果显示突变体胚乳中AGPS1、AGPL2、GBSSI、SSI、SSIIa、SBEI、SBEIIa、ISA1和PUL的表达量显著低于野生型。

A white-core endosperm mutant, M30, was screened from the Kitaake mutant library induced by 60Co radiation. The width, thickness, and weight of brown rice decreased significantly in M30. The total starch content decreased, but the storage protein increased in the brown kernel flour of M30. Compared with WT, starch from M30 had significantly lower amylose content, and exhibited lower hot viscosity, breakdown viscosity, final viscosity and gelatinization temperature. The compound starch granules in the central part of endosperm were markedly reduced in number, and had a large number of small starch granules with loosely-packed arrangement. The mutation gene was mapped to 64.9 kb of chromosome 10 using the opaque endosperm recessive individuals isolated from M30/Dular population. The region contained seven open reading frames(ORFs), in which ORF4 encoded rice alanine aminotransferase 1(OsAlaAT1). Sequencing revealed that only 872 bp of OsAlaAT1 genome sequence was missing in the mutant. The InDel marker designed by this mutation site co-segregated with the opaque endosperm individuals in the mapping population, while 22 conventional rice varieties did not contain the mutation site. The qRT-PCR experiments revealed that the expression levels of AGPS1, AGPL2, GBSSI, SSI, SSIIa, SBEI, SBEIIa, ISA1 and PUL in mutant endosperm were significantly lower than those in wild type.