Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and ch...Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 （spcl-1） and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase （ZDS） in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.展开更多
Using a phylogenomic approach, we have identified and subciassified a new family of carotenoid-binding proteins. These proteins have sequence homology to the N-terminal domain （NTD） of the Orange Carotenoid Protein ...Using a phylogenomic approach, we have identified and subciassified a new family of carotenoid-binding proteins. These proteins have sequence homology to the N-terminal domain （NTD） of the Orange Carotenoid Protein （OCP）, and are referred to as Helical Carotenoid Proteins （HCPs）. These proteins comprise at least nine distinct ciades and are found in diverse organisms, frequently as multiple paralogs representing the distinct ciades. These seem to be out-paralogs maintained from ancient duplications associated with subfunctionalization. All of the HCPs share conservation of the residues for carotenoid binding, and we confirm that carotenoid binding is a fundamental property of HCPso We solved two crystal structures of the Nostoc sp. PCC 7120 HCP1 protein, each binding a different carotenoid, suggesting that the proteins flexibly bind a range of carotenoids. Based on a comprehensive phylogenetic analysis, we propose that one of the HCP subtypes is likely the evolutionary ancestor of the NTD of the OCP, which arose following a domain fusion evenS. However, we predict that the majority of HCPs have functions distinct from the NTD of the OCP. Our results demonstrate that the HCPs are a new family of functionally diverse carotenoid-binding proteins found among ecophysiologically diverse cyanobacteria.展开更多
基金grants from National Natural Science Foundation of China （Grant Nos. 30330360, 30125025 , 30221002） Chinese Academy of Sciences （Grant No. KSCX2- YW-N-015）
文摘Carotenoids, a class of natural pigments found in all photosynthetic organisms, are involved in a variety of physiological processes, including coloration, photoprotection, biosynthesis of abscisic acid （ABA） and chloroplast biogenesis. Although carotenoid biosynthesis has been well studied biochemically, the genetic basis of the pathway is not well understood. Here, we report the characterization of two allelic Arabidopsis mutants, spontaneous cell death1-1 （spcl-1） and spc1-2. The weak allele spc1-1 mutant showed characteristics of bleached leaves, accumulation of superoxide and mosaic cell death. The strong mutant allele spc1-2 caused a complete arrest of plant growth and development shortly after germination, leading to a seedling-lethal phenotype. Genetic and molecular analyses indicated that SPC1 encodes a putative ζ-carotene desaturase （ZDS） in the carotenoid biosynthesis pathway. Analysis of carotenoids revealed that several major carotenoid compounds downstream of SPC 1/ZDS were substantially reduced in spc1-1, suggesting that SPC 1 is a functional ZDS. Consistent with the downregulated expression of CAO and PORB, the chlorophyll content was decreased in spc1-1 plants. In addition, expression of Lhcb1. 1, Lhcbl. 4 and RbcS was absent in spc1-2, suggesting the possible involvement of carotenoids in the plastid-to-nucleus retrograde signaling. The spc1-1 mutant also displays an ABA-deficient phenotype that can be partially rescued by the externally supplied phytohormone. These results suggest that SPC1/ZDS is essential for biosynthesis of carotenoids and plays a crucial role in plant growth and development.
基金The work in the Kerfeld Laboratory was supported by the National Science Foundation （lOS 1557324） and by the Office of Science of the U.S. Depart- ment of Energy DE-FG02-91ER20021. The research in D.K.＇s laboratory was supported by grants from the Agence Nationale de la Recherche （ANR, project CYANOPROTECT）, the Centre National de la Recherche Scientifique （CNRS） and the Commissariat ＆ I＇Energie Atomique.ACKNOWLEDGMENTS We thank Prof. C. Peter Wolk （MSU-DOE Plant Research Laboratory and Department of Plant Biology, Michigan State University） for the gift of E, coil strain ED8654 and pRL443 plasmid. We are indebted to Dr. Enrique Ftores and Dr. Antonia Herrero （IBVF, Seville, Spain） for the Nostoc 7120 strain and the pRL277 plasmid. We thank Dr. Fei Cai for comments and assistance in revision of this manuscript. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231 No conflict of interest declared.
文摘Using a phylogenomic approach, we have identified and subciassified a new family of carotenoid-binding proteins. These proteins have sequence homology to the N-terminal domain （NTD） of the Orange Carotenoid Protein （OCP）, and are referred to as Helical Carotenoid Proteins （HCPs）. These proteins comprise at least nine distinct ciades and are found in diverse organisms, frequently as multiple paralogs representing the distinct ciades. These seem to be out-paralogs maintained from ancient duplications associated with subfunctionalization. All of the HCPs share conservation of the residues for carotenoid binding, and we confirm that carotenoid binding is a fundamental property of HCPso We solved two crystal structures of the Nostoc sp. PCC 7120 HCP1 protein, each binding a different carotenoid, suggesting that the proteins flexibly bind a range of carotenoids. Based on a comprehensive phylogenetic analysis, we propose that one of the HCP subtypes is likely the evolutionary ancestor of the NTD of the OCP, which arose following a domain fusion evenS. However, we predict that the majority of HCPs have functions distinct from the NTD of the OCP. Our results demonstrate that the HCPs are a new family of functionally diverse carotenoid-binding proteins found among ecophysiologically diverse cyanobacteria.
