期刊
JOURNAL OF EXPERIMENTAL BOTANY
卷 65, 期 13, 页码 3623-3636出版社
OXFORD UNIV PRESS
DOI: 10.1093/jxb/eru234
关键词
Crassulacean acid metabolism; gene duplication; Orchidaceae; Oncidiinae; phosphoenolpyruvate carboxylase; photosynthesis
资金
- Smithsonian Tropical Research Institute
- US Environmental Protection Agency [MA 91685201]
- National Science Foundation NSF [IOB-0543659]
- National Institute of Health (NIH) from the INBRE Program of the National Center for Research Resources through Nevada Genomics, Proteomics, and Bioinformatics Centers [P20 RR-016464]
Phosphoenolpyruvate carboxylase (PEPC) catalyses the initial fixation of atmospheric CO2 into oxaloacetate and subsequently malate. Nocturnal accumulation of malic acid within the vacuole of photosynthetic cells is a typical feature of plants that perform crassulacean acid metabolism (CAM). PEPC is a ubiquitous plant enzyme encoded by a small gene family, and each member encodes an isoform with specialized function. CAM-specific PEPC isoforms probably evolved from ancestral non-photosynthetic isoforms by gene duplication events and subsequent acquisition of transcriptional control elements that mediate increased leaf-specific or photosynthetic-tissue-specific mRNA expression. To understand the patterns of functional diversification related to the expression of CAM, ppc gene families and photosynthetic patterns were characterized in 11 closely related orchid species from the subtribe Oncidiinae with a range of photosynthetic pathways from C-3 photosynthesis (Oncidium cheirophorum, Oncidium maduroi, Rossioglossum krameri, and Oncidium sotoanum) to weak CAM (Oncidium panamense, Oncidium sphacelatum, Gomesa flexuosa and Rossioglossum insleayi) and strong CAM (Rossioglossum ampliatum, Trichocentrum nanum, and Trichocentrum carthagenense). Phylogenetic analysis revealed the existence of two main ppc lineages in flowering plants, two main ppc lineages within the eudicots, and three ppc lineages within the Orchidaceae. Our results indicate that ppc gene family expansion within the Orchidaceae is likely to be the result of gene duplication events followed by adaptive sequence divergence. CAM-associated PEPC isoforms in the Orchidaceae probably evolved from several independent origins.
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