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水稻是最重要的粮食作物之一,提高水稻产量一直是育种的主要目标。水稻四倍体相对于二倍体具有籽粒变大、粒重增加的特点,研究基因组加倍后籽粒大小基因的调控模式,在育种应用方面具有十分重要的意义。本文以二倍体-四倍体水稻为材料,分析6个控制籽粒大小基因在幼穗发育中的表达差异,同时结合转基因实验,探讨基因剂量增加对基因表达水平和籽粒大小的影响。结果发现:基因组加倍后,水稻的发育进程不变,但株高增加,叶片变宽,籽粒变大,增大后的籽粒在籼稻表现为长、宽均增加显著,而在粳稻中长度比宽度增加更为明显。进一步分析控制籽粒大小基因的表达差异情况,发现这些基因的表达不仅受发育时期的影响,在籼粳亚种间也明显不同,即受遗传背景的影响。在基因组加倍的情况下,正调控基因GS5、HGW的表达普遍高于对应的二倍体;负调控基因GS3在籼稻D9311中趋于下调或沉默,而在粳稻DBl中趋于上调,GW2在D9311中上调,而在DBl中趋于沉默。通过转基因实验分析负调控基因GW2在二倍体Bl中的表达趋势,发现其在基因剂量线性增加的情况下,表达水平高于二倍体和四倍体,导致其籽粒变小。本研究结果有助于了解水稻中控制籽粒大小的基因在二倍体和四倍体中的表达模式,为高产育种提供理论依据。
Rice is one of the most important food crops and increasing rice production has been the main goal of breeding. The tetraploid rice has the characteristics of larger grain size and heavier grain weight than diploid, and it is very important to study the regulation mode of gene size after doubling genome. In this paper, the diploid-tetraploid rice was used as the material to analyze the differences of six genes controlling seed size in panicle development. The effects of gene dosage on the gene expression and grain size were also studied. The results showed that: after doubling the genome, the developmental process of rice did not change, but the plant height increased, the leaves widened and the kernels became larger. The increased kernels of indica rice showed a significant increase in length and width, while the ratio of length to breadth Increase more obvious. Further analysis of the differences in the control of grain size genes revealed that the expression of these genes was not only affected by developmental stages but also significantly different between indica and japonica subspecies, ie influenced by genetic background. In the case of doubling of the genome, the expression of GS5 and HGW is generally higher than that of the corresponding diploid. The negative regulation gene GS3 is down-regulated or silenced in indica rice D9311, but up-regulated in japonica rice DB1 while GW2 is in D9311 In the increase, while in the DBl tends to be silent. The expression of GW2, a negative regulatory gene in diploid Bl, was analyzed by transgenic experiment. The results showed that the expression level of GW2 was higher than that of diploid and tetraploid under the condition of linear increase in gene dosage, resulting in smaller grains. The results of this study are helpful to understand the expression pattern of the genes controlling grain size in rice, in diploid and tetraploid, and provide the theoretical basis for high-yielding breeding.