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Advances in Photosynthesis Fundamental Aspects Part 8

Tham khảo tài liệu 'advances in photosynthesis fundamental aspects part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 202 Advances in Photosynthesis - Fundamental Aspects Yamashino et al. 2003 . However thorough analysis of PIF3 function has led to the conclusion that it does not play a significant role in controlling light input to the circadian clock Viczian et al. 2005 . Indeed there is circumstantial evidence of phytochromes regulating CCA1 and LHY. Both genes are rapidly induced in a TOC1 dependent manner upon transfer of dark grown seedlings to red light. This induction requires EARLY FLOWERING 4 ELF4 which forms with CCA1 and LHY a negative feedback loop in an analogous manner to TOC1 Kikis et al. 2005 and ELF4 is itself a direct target of FHY3 FAR1 and HY5 Li et al. 2011 . ELF3 is also necessary for light-induced expression of CCA1 and LHY and this event seems to occur indirectly through a direct repression of PRR9 by physically interacting with its promoter Dixon et al. 2011 . 5. Downstream targets of light and clock signalling 5.1 The impact of the circadian clock in the expression of photosynthesis related genes As presented above the interconnections between the clock and light signalling are extremely complex. The regulation of outputs is not an exception. One unbiased measure of the impact of the circadian clock on plant development is the finding that at least one third of the Arabidopsis genome is circadian regulated Covington et al. 2008 . The genes involved in photosynthesis are an important target group of the circadian clock and tend to be expressed at the middle of the subjective day together with genes involved in the phenylpropanoid pathway Edwards et al. 2006 . In another global analysis it was shown that PRR5 PRR7 and PRR9 are negative regulators of the chlorophyll and carotenoid biosynthetic pathways Fukushima et al. 2009 . Despite what we know of the clock impact on photosynthetic gene expression the mechanisms are still poorly understood. One such mechanism may involve CCA1. CCA1 was originally identified by its binding to an AA CA AATCT motif in the .