Functional Changes of Red/Far-Red Light Photoreceptor Phytochrome A with Loss of Photosynthesis in Parasitic Plants (pp. 133-148)
Authors: (Kazuteru Takagi, Atsushi Okazawa, Graduate School of Engineering, Osaka University, Osaka, Japan)
Abstract: Parasitic plants constitute 1% (ca, 4,500 species) of angiosperms and are classified into two categories. One is hemiparasite, which retains photosynthetic ability, another is holoparasite, which had lost photosynthetic ability and acquires all their carbon sources from their host plants. Because holoparasites had been lost photosynthetic ability, the selective pressure to maintain photosynthesis had been reduced significantly. Therefore in holoparasites photoresponses which are important to optimize photosynthesis are not necessary. On the other hand, photoresponses are also involved in the regulation of plant development such as germination and flowering. Studies on photoresponses of parasitic plants revealed that the pattern of their photoresponses has altered to adapt to their parasitic life cycles. Molecular analysis of their red/far-red light photoreceptor phytochrome suggested the relationships between the alternation of their amino acid sequences and its molecular function.