Molecular studies of clock proteins, LWD1 and LWD2, in Arabidopsis circadian rhythm

• Main Authors: Ying Wang, 王瑛
• Other Authors: Shu-Hsing Wu
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/31229142866848053018

博士 === 國防醫學院 === 生命科學研究所 === 99 === In plants, circadian clock could control day-length-dependent developmental processes such as photoperiodic flowering. The Arabidopsis circadian clock is formed by several negative feedback loops composed of oscillator genes expressing at specific time during a day. The identification of additional clock genes will help to better dissect the complex nature of the circadian clock. Here we show light-regulated WD repeats protein 1 (LWD1) and LWD2 are new clock genes regulating photoperiodic flowering and circadian period length. LWD1 and LWD2 proteins share 91.4 % identity in amino acid sequence. The lwd1 lwd2 double mutant has an early flowering phenotype, and a short period length for its internal clock under free running condition. Analysis of the lwd1 lwd2 double mutant also revealed that LWD1/2 plays dual functions in the light input pathway and the regulation of the central oscillator. Promoter:luciferase fusion studies showed that transcriptional activities of LWD1/2 are rhythmic and depend on functional PRR9 and PRR7. LWD1/2 is also needed for the expression of PRR9, PRR7 and PRR5. LWD1 is preferentially localized within the nucleus and associates with promoters of PRR9, PRR5 and TOC1 in vivo. Our results support the existence of a positive feedback loop within the Arabidopsis circadian clock. Further mechanistic studies of this positive feedback loop and its regulatory effects on the other clock components will further elucidate the complex nature of the Arabidopsis circadian clock.