title: Cloning and functional analysis of 9-cis-epoxycarotenoid dioxygenase (NCED) genes encoding a key enzyme during abscisic acid biosynthesis from peach and grape fruits.
abstract: Ripening and senescence are generally controlled by ethylene in climacteric fruits like peaches, and the ripening process of grape, a non-climacteric fruit, may have some relationship to abscisic acid (ABA) function. In order to better understand the role of ABA in ripening and senescence of these two types of fruits, we cloned the 9-cis-epoxycarotenoid dioxygenase (NCED) gene that encodes a key enzyme in ABA biosynthesis from peaches and grapes using an RT-PCR approach. The NCED gene fragments were cloned from peaches (PpNCED1and PpNCED2, each 740bp) and grapes (VVNCED1, 741bp) using degenerate primers designed based on the conserved amino acids sequence of NCEDs in other plants. PpNCED1 showed 78.54% homology with PpNCED2, 74.90% homology with VVNCED1, and both showed high homology to NCEDs from other plants. The expression patterns of PpNCED1 and VVNCED1 were very similar. Both were highly expressed at the beginning of ripening when ABA content becomes high. The maximum ABA preceded ethylene production in peach fruit. ABA in the grape gradually increased from the beginning of ripening and reached the highest level at 20d before the harvest stage. However, ethylene remained at low levels during the entire process of fruit development, including ripening and senescence. ABA content, and ripening and softening of both types of fruits, were promoted or delayed by exogenous ABA or Fluridone (or NDGA) treatment. The roles of ABA and ethylene in the later ripening of fruit are complex. Based on results obtained in this study, we concluded that PpNCED1 and VVNCED1 initiate ABA biosynthesis at the beginning of fruit ripening, and that ABA accumulation might play a key role in the regulation of ripeness and senescence of both peach and grape fruits.
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University, Beijing 100094, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Zhang
authors.affiliation: College of Agronomy and Biotechnology, China Agricultural University, Beijing 100094, China. Electronic address: pleng@cau.edu.cn.
authors.forename: Ping
authors.initials: P
authors.lastname: Leng
authors.affiliation: Beijing Municipal Science and Technology Commission, Beijing 100035, China.
authors.forename: Guanglian
authors.initials: G
authors.lastname: Zhang
authors.affiliation: Beijing Municipal Science and Technology Commission, Beijing 100035, China.
authors.forename: Xiangxin
authors.initials: X
authors.lastname: Li
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis* / Q000494:pharmacology; D000595:Amino Acid Sequence; D000598:Amino Acids, Cyclic / Q000494:pharmacology; D003001:Cloning, Molecular; D003521:Cyclopropanes / Q000494:pharmacology; D049308:Dioxygenases; D005030:Ethylenes / Q000096:biosynthesis; D005638:Fruit / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D008969:Molecular Sequence Data; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins; D027861:Prunus / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D011728:Pyridones / Q000494:pharmacology; D017422:Sequence Analysis, DNA; D027843:Vitis / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development
chemical_list: D000598:Amino Acids, Cyclic; D003521:Cyclopropanes; D005030:Ethylenes; D010940:Plant Proteins; D011728:Pyridones; C023863:1-aminocyclopropane-1-carboxylic acid; C013351:fluridone; D000040:Abscisic Acid; C036216:ethylene; D010105:Oxygenases; D049308:Dioxygenases; C109043:9-cis-epoxy-carotenoid dioxygenase; C412563:1-methylcyclopropene