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, GA4/7 upregulated 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.

DNA Damage Inducible Protein 1 is Involved in Cold Adaption of Harvested Cucumber Fruit

“…Total RNA from cucumber peels or Arabidopsis plants were extracted using Trizol reagent (Invitrogen, USA) according to the manufacturer's instructions (Zhang et al, 2016b). The concentration and quality of total RNA was determined by spectrophotometry and visualized using 1.1% agarose gel.…”

“…The construct pCAMBIA 2300-CsDDI1 was then electroporated into GV3101 and transformed into Arabidopsis using the floral dip method (Zhang et al, 2006). The seeds were harvested and then sown onto MS selection medium containing kanamycin (50 mg/ml) for identification of the transgenic plants using the method as described previously (Zhang et al, 2016b). Two independent 35S::CsDDI1 overexpression lines were obtained.…”

“…Phenotype analysis was performed as we described previously (Zhang et al, 2016b). Germination assays were carried out on three replicates of 50 seeds.…”

Genetic Improvement of Tropical and Subtropical Fruit Trees via Biolistic Methods

“…One of the physiological disorders which limited the industry of the pineapple in different area productions in the world such as Australia is the internal browning or blackheart. This disorder causes severe loss when appearing at conditions with day/night temperatures below 25/20°C with low light during fruit development and also during storage and shipment [32,33]. To control the internal browning by the molecular breeding methods, an effort was made by [32] in order to obtain a transgene resistant to blackheart through biolistic method.…”

“…The leaf callus of Smooth Cayenne cultivar was bombarded with gold particles coated with pART7 plasmid harboring PINPPO1 gene (pineapple polyphenol oxidase gene) which could successfully attain resistant plants to blackheart with an efficiency of 0.21-1.5% based on the PCR and Southern blot analysis ( Table 1). Recent studies demonstrated that low temperature (5°C) could reduce blackheart through upregulated AcGA2ox gene and reduce GA 4 levels compared to the higher temperature (20°C) [33]. Also, the Del Monte Foods company introduces a red-fleshed pineapple "Rosé" by overexpression/suppression of some genes related to lycopene accumulation [34].…”