Polyphenol oxidase is induced by chilling and wounding in pineapple

Abstract

Polyphenol oxidase (PPO) activity was found to be low in the leaves, roots, inflorescence tissues and developing and mature fruit of pineapple (Ananas comosus L.). In fruit affected by the chill-induced internal browning disorder known as Blackheart, PPO activity was 10-fold higher than in unaffected fruit, and there was a direct correlation between PPO activity and the severity of Blackheart symptoms. Degenerate oligonucleotide primers were designed to conserved regions of plant PPO genes, and used to amplify two distinct pineapple PPO cDNAs, designated PINPPO1 (2181 bp) and PINPPO2 (1319 bp), which share 81% sequence identity at the DNA level and show a high degree of homology to other plant PPO genes. PINPPO1 encodes a peptide of 604 amino acids, including a putative transit peptide of 95 amino acids and two copper-binding regions, CuA and CuB, which are highly conserved in plant PPOs. Southern analysis suggested the presence of at least four PPO genes in pineapple. Expression of PINPPO1 and PINPPO2 was low in roots, leaves, inflorescence tissues and developing fruit, but was strongly up-regulated in response to chilling and wounding. These results indicate that PPO is synthesised de novo in response to chilling of pineapple fruit, and implicate a role for the enzyme in the development of Blackheart disorder.

Molecular cloning and characterisation of banana fruit polyphenol oxidase

“…Boss et al (1995) reported wound-induced accumulation of PPO mRNA in apple fruit and Stewart et al (2001) recently demonstrated that PPO is induced in both leaves and fruit of pineapple following wounding. However, we detected no signi®cant wound induced increases in PPO activity in banana¯esh over a 72-h period (Fig.…”

The polyphenol oxidase gene family in poplar: phylogeny, differential expression and identification of a novel, vacuolar isoform

“…5). Apple pAPO5 (Boss et al 1995) and pineapple PINPPO1 and PINPPO2 (Stewart et al 2001) are two other wound-inducible PPO genes. Interestingly, these wound-induced PPOs from diVerent species do not cluster together in the phylogenetic analysis (Fig.…”

“…Five and seven PPO genes were isolated from these crop plants, respectively, and are primarily expressed in fruit, Xowers, and leaves (Hunt et al 1993;Shahar et al 1992;. Although generally constitutively found throughout the plant, PPO activity is often up-regulated in wounded tissues, and thus, PPOs are often considered to be plant defense proteins (Boss et al 1995;Constabel et al 1995;Pinto et al 2008;Stewart et al 2001;Thipyapong et al 1995). However, the physiological functions of PPOs are likely much more diverse.…”

The Introduction of Transgenes to Control Blackheart in Pineapple (Ananas Comosus L.) cv. Smooth Cayenne by Microprojectile Bombardment

“…Of the pineapple ppo genes isolated by Stewart et al (2001), constructs were designed containing the PINPPO1 gene in a sense (ppo) and sense/antisense (opp.ppo) orientation in pART7. The sense construct was controlled by the CaMV35S promoter and has an ocs terminator.…”

“…In pineapple it has been shown that the occurrence of blackheart is directly associated with the oxidation of phenolics by ppo (Stewart et al 2001). Our strategy is based on the molecular suppression of ppo activity, using the optimised and efficient biolistic protocol.…”