| Summary: | 碩士 === 國立臺灣大學 === 植物科學研究所 === 106 === MOS4 (Modifier of SNC1, 4) is the core protein of the MOS4-associated complex (MAC) involved in mRNA splicing in Arabidopsis. The function of MAC in pathogen resistance has been well studied. However, the pleotropic developmental defects in the mutants of MAC members imply that MAC may also participate in many processes of plant development. Here, we found that the mos4 knock-out mutants are insensitive to photoperiod. mos4 plants display a late flowering phenotype under long-day conditions but are early flowering under short-day conditions. The expression phase of the circadian output GIGANTEA (GI) is shifted in mos4 mutants, resulting delayed expression of the flowering activator CONSTANS (CO). Consequently, the flowering integrator FLOWERING LOCUS T (FT) maintains in a low expression level in the evening. The morning loop genes are essential for maintaining the circadian clock in plants and their expression is delayed about 3 hours in mos4 mutants. Two of the morning loop members, PSEUDO-RESPONSE REGULATORS7 (PRR7) and PRR9, were further analyzed on their alternative splicing events. The alternatively spliced transcripts of PRR7 and PRR9 are increased in mos4 mutants. Taken together, our studies indicate that MOS4 may play an essential role in flowering time control through regulating the splicing of circadian clock genes.
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