Generation of a rice mutant library by shotgun antisense gene silencing and mutant screening

A strategy of shotgun antisense gene silencing was used to generate a rice mutant library. A total of (1 486) transgenic rice plants were obtained from 105 independent Hygromycin(Hm) resistant calli transformed with rice antisense cDNA library, using japonica cultivar Zhonghua 11 as transformation material. A total of 335 T_0 transformants from 11 independent calli were selected randomly to test Hm resistance by leaf segments screening. The results showed that all T_0 plants tested were Hm resistant, coincident with the results of PCR analysis, indicating that no escapee existed in T_0 transformants. The result of Southern blot analysis revealed that most of the transgenic plants contained single T-DNA insertion. Some morphological variations were observed in T_0 and T_1 transgenic plants such as dwarf, non-tiller or multi-tillers, decrease of seed-setting, changes of grain or panicle shape or spikelet structure. One mutant was characterized, the mutative traits of which cosegregated with Hm resistance. The mutant displayed about 50% decrease of seed-setting rate and 40% decrease of total number of spikelets per panicle, resulting in about 70% decrease of seed production per panicle as compared with non-transgenic control.