title: Mechanism of internal browning of pineapple: The role of gibberellins catabolism gene (AcGA2ox) and GAs.
abstract: Internal browning (IB), a physiological disorder (PD) that causes severe losses in harvested pineapple, can be induced by exogenous gibberellins (GAs). Over the years, studies have focused on roles of Gibberellin 2-oxidase (GA2oxs), the major GAs catabolic enzyme in plants, in the regulation of changes in morphology or biomass. However, whether GA2oxs could regulate PD has not been reported. Here, a full-length AcGA2ox cDNA was isolated from pineapple, with the putative protein sharing 23.59% to 72.92% identity with GA2oxs from five other plants. Pineapples stored at 5 °C stayed intact, while those stored at 20 °C showed severe IB. Storage at 5 °C enhanced AcGA2ox expression and decreased levels of a GAs (GA4) 'compared with storage at 20 °C. However, at 20 °C, exogenous application of abscisic acid (ABA) significantly suppressed IB. ABA simultaneously upregulated AcGA2ox and reduced GA4. Ectopic expression of AcGA2ox in Arabidopsis resulted in reduced GA4, lower seed germination, and shorter hypocotyls and roots, all of which were restored by exogenous GA4/7. Moreover, in pineapple, GA4/7upregulated polyphenol oxidase, while storage at 5 °C and ABA downregulated it. These results strongly suggest the involvement of AcGA2ox in regulation of GAs levels and a role of AcGA2ox in regulating IB.
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.
authors.forename: Xiuwen
authors.initials: X
authors.lastname: Rao
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.|South Subtropical Crops Research Institute, Chinese Academy of Tropical Agricultural Sciences/Hainan Key Laboratory for Postharvest Physiology and Technology of Tropical Horticultural Products, Zhanjiang 524091, Guangdong Province, China.
authors.forename: Lubin
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.
authors.forename: Congcong
authors.initials: C
authors.lastname: He
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Yang
authors.affiliation: Guangdong Province Key Laboratory of Postharvest Physiology and Technology of Fruits and Vegetables, College of Horticulture, South China Agricultural University, Guangzhou 510642, Guangdong Province, China.
authors.forename: Shijiang
authors.initials: S
authors.lastname: Zhu
mesh_terms: D000040:Abscisic Acid / Q000235:genetics / Q000378:metabolism; D031230:Ananas / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics; D005875:Gibberellins / Q000235:genetics* / Q000378:metabolism; D008660:Metabolism / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000235:genetics*; D010935:Plant Diseases / Q000235:genetics*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D005875:Gibberellins; D000040:Abscisic Acid; D006899:Mixed Function Oxygenases; C121463:gibberellin 2-dioxygenase