Induced splice site mutation generates alternative intron splicing in starch synthase II (SSII) gene in rice

Abstract

The evolution of starch synthase (SS) has been extensively analysed in the model plant rice, but there have been few detailed studies directed towards exploring the intron splicing variant effect on the divergence of the SS gene. We report here an example that the alternative splicing of a GC-AG intron induced a new splicing isoform of SSII-1 expressed in Oryza sativa japonica cultivar Zhonghua-15. In addition, a GT-AG intron flanking the alternative splicing GC-AG intron was simultaneously spliced at an incorrect position, inducing another intron fragment gained in mature SSII-1 RNA. Moreover, when a GT-AG intron from SSII-3 was artificially mutated into the GC-AG intron, a 28 bp fragment from the intron added to the mature RNA could be observed in transgenic rice. In this study, the alternative intron splicing of the GC-AG intron might offer more variants for genetic divergence of the starch synthase gene family in rice.