Molecular cloning and characterisation of banana fruit polyphenol oxidase

Abstract

Polyphenol oxidase (PPO; EC 1.10.3.2) is the enzyme thought to be responsible for browning in banana [Musa cavendishii (AAA group, Cavendish subgroup) cv. Williams] fruit. Banana flesh was high in PPO activity throughout growth and ripening. Peel showed high levels of activity early in development but activity declined until ripening started and then remained constant. PPO activity in fruit was not substantially induced after wounding or treatment with 5-methyl jasmonate. Banana flowers and unexpanded leaf roll had high PPO activities with lower activities observed in mature leaves, roots and stem. Four different PPO cDNA clones were amplified from banana fruit (BPO1, BPO11, BPO34 and BPO35). Full-length cDNA and genomic clones were isolated for the most abundant sequence (BPO1) and the genomic clone was found to contain an 85-bp intron. Introns have not been previously found in PPO genes. Northern analysis revealed the presence of BPO1 mRNA in banana flesh early in development but little BPO1 mRNA was detected at the same stage in banana peel. BPO11 transcript was only detected in very young flesh and there was no detectable expression of BPO34 or BPO35 in developing fruit samples. PPO transcripts were also low throughout ripening in both flesh and peel. BPO1 transcripts were readily detected in flowers, stem, roots and leaf roll samples but were not detected in mature leaves. BPO11 showed a similar pattern of expression to BPO1 in these tissues but transcript levels were much lower. BPO34 and BPO35 mRNAs were only detected at a low level in flowers and roots and BPO34 transcript was detected in mature leaves, the only clone to do so. The results suggest that browning of banana fruit during ripening results from release of pre-existing PPO enzyme, which is synthesised very early in fruit development.

Characterization of rice polyphenol oxidase promoter in transgenic Arabidopsis thaliana

“…Similar results were found in Glycine max PPO gene promoter, which showed 2.5-fold upregulation by ABA but not by MeJ (Chai et al, 2013). Moreover, banana PPO gene also remained unresponsive to MeJ (Gooding et al, 2001). Recently, ABA signal transduction was found to be involved in regulation of stomatal opening and closure to control pathogen and drought stress (Lim et al, 2015), which may indicate a possible involvement of OsPPO in plant defense through ABA signaling.…”

Independent Losses of Function in a Polyphenol Oxidase in Rice: Differentiation in Grain Discoloration between Subspecies and the Role of Positive Selection under Domestication

“…Within this DNA segment, 14 open reading frames (ORFs) have been predicted ( Figure 2C) (Feng et al, 2002). Among them, OSJNBa0053K19.18 (referred to as K18 hereafter) is highly similar to plant PPO genes (Cary et al, 1992;Chevalier et al, 1999;Constabel et al, 2000;Gooding et al, 2001;Demeke and Morris, 2002). The similarity in protein sequence ranges from 43 to 68%, and the highest is found with wheat PPO.…”

Banana Peel Physiological Post-Harvest Disorders: A Review

“…Thus, a membrane damage is needed to put into contact these components in order to induce catalyze reaction. Banana peel browning would result of pre-existing free phenolic compounds release [24]. It's correlated with an increase in the production of phenyl-ammonia-lyase (PAL) and poly phenol-oxidase (PPO) and a decrease of both the total free phenolic compounds and anthocyanins [25].…”