Inheritance And Expression Of The Antisense Wx Gene In Transgenic Rice And Its Influence On Rice Quality And Yield

Amylose content in rice endosperm is one of the key determinants of rice eating and cooking quality, and the poor quality is closely related to the high amylose level in rice grains. Antisense RNA strategy is an efficient way to down-regulate the amylose content in rice endosperm, in our previous studies, the antisense Wx gene had been introduced into several elite rice varieties both of japonica and indica, and lots of transgenic rice plants or lines with reduced amylose level had been selected. Then, it is important to understand the inheritance and expression of the antisense Wx gene in the progeny of transgenic rice and the potential of using these transgenic materials in rice breeding. In present studies, several transgenic rice lines or plants with different amylose content were used for genetic analysis and field-testing. The main results were showed in the followings:(1) The waxy or low amylose character, induced by the introduced antisense Wx gene, was dominant, which differed from the recessive of the natural waxy mutant.(2) Genetic analysis demonstrated that the antisense Wx gene and improved amylose content are stably inherited (up to ninth generation) in these transgenic lines.(3) It was interesting to observe that there was a relationship among the three cooking and eating quality factors, means that when the amylose content in the seeds of transgenic plants reduced, the gel consistency decreased, while the gelatinization temperature increased, especially the alteration of the gel consistency was significant. There was also a relationship between the amylose content and the RVA characters, the relativity reached 0.97 between the level of cold stickiness and the amylose content.(4) The effect of reduced amylose content on kernel weight in transgenic rice wascarefully investigated. It was found that waxy kernels were lighter than non-waxy ones in all the three transgenic lines, in which the amylose content has been reduced from 17% to around 2%. The relative difference of weight between waxy and non-waxy kernels was 6%~8%, which was significantly correlated to the degree of reduction in apparent amylose content, and this difference was relatively stable in successive generations. The results from field-testing showed that the level of reduction in yielding was less than that of the kernel weight, the high yielding potential of the parents could be remained in these transgenic waxy rice lines. These results implied that it was an effective way to breeding quality rice with high yielding, especially high-yielding waxy rice varieties by transgenic approach.(5) The agronomic traits of several elite transgenic lines were carefully investigated in the fields. Most of the transgenic plants showed characteristics similar to those of the original cultivars, except the grain weight.(6) Using the transgenic rice lines as the parents, the indica hybrid containing the antisense Wx gene were produced, and the amlose content of rice grains in their F2 generation was also decreased, indicated that it was a useful approach to improve the grain quality of hybrid rice through genetic engineering.