title: Dissecting the role of climacteric ethylene in kiwifruit (Actinidia chinensis) ripening using a 1-aminocyclopropane-1-carboxylic acid oxidase knockdown line.
abstract: During climacteric fruit ripening, autocatalytic (Type II) ethylene production initiates a transcriptional cascade that controls the production of many important fruit quality traits including flavour production and softening. The last step in ethylene biosynthesis is the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene by the enzyme ACC oxidase (ACO). Ten independent kiwifruit (Actinidia chinensis) lines were generated targeting suppression of fruit ripening-related ACO genes and the fruit from one of these lines (TK2) did not produce detectable levels of climacteric ethylene. Ripening behaviour in a population of kiwifruit at harvest is asynchronous, so a short burst of exogenous ethylene was used to synchronize ripening in TK2 and control fruit. Following such a treatment, TK2 and control fruit softened to an 'eating-ripe' firmness. Control fruit produced climacteric ethylene and softened beyond eating-ripe by 5 d. In contrast, TK2 fruit maintained an eating-ripe firmness for >25 d and total volatile production was dramatically reduced. Application of continuous exogenous ethylene to the ripening-arrested TK2 fruit re-initiated fruit softening and typical ripe fruit volatiles were detected. A 17 500 gene microarray identified 401 genes that changed after ethylene treatment, including a polygalacturonase and a pectate lyase involved in cell wall breakdown, and a quinone oxidoreductase potentially involved in volatile production. Many of the gene changes were consistent with the softening and flavour changes observed after ethylene treatment. However, a surprisingly large number of genes of unknown function were also observed, which could account for the unique flavour and textural properties of ripe kiwifruit.
authors.affiliation: New Zealand Institute for Plant and Food Research Ltd , Auckland, New Zealand. ross.atkinson@plantandfood.co.nz
authors.forename: Ross G
authors.initials: RG
authors.lastname: Atkinson
authors.forename: Kularajathevan
authors.initials: K
authors.lastname: Gunaseelan
authors.forename: Mindy Y
authors.initials: MY
authors.lastname: Wang
authors.forename: Luke
authors.initials: L
authors.lastname: Luo
authors.forename: Tianchi
authors.initials: T
authors.lastname: Wang
authors.forename: Cara L
authors.initials: CL
authors.lastname: Norling
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Johnston
authors.forename: Ratnasiri
authors.initials: R
authors.lastname: Maddumage
authors.forename: Roswitha
authors.initials: R
authors.lastname: Schröder
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Schaffer
mesh_terms: D029042:Actinidia / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D000594:Amino Acid Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D020451:Contig Mapping; D018076:DNA, Complementary / Q000235:genetics; D005030:Ethylenes / Q000378:metabolism; D005638:Fruit / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010937:Plant Growth Regulators / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified; D017422:Sequence Analysis, DNA
chemical_list: D018076:DNA, Complementary; D005030:Ethylenes; D010937:Plant Growth Regulators; D010940:Plant Proteins; C036216:ethylene; D000594:Amino Acid Oxidoreductases; C059460:1-aminocyclopropane-1-carboxylic acid oxidase