Gene expression of antioxidant enzymes and coffee seed quality during pre- and post-physiological maturity

Seeds collected at different maturation stages vary in physiological quality and patterns of protective antioxidant systems against deterioration. In this study we investigated the expression of genes that codify catalase (CAT), dismutase superoxide (SOD), and polyphenol oxidase (PPO) during the pre- and post-physiological maturation phases in whole seeds and in endosperms and embryos extracted from the seeds. Coffea arabica L. berries were collected at the green, yellowish-green, cherry, over-ripe, and dry stages, and the seeds were examined physiologically. The transcription levels of the genes were quantified by quantitative real-time polymerase chain reaction using coffee-specific primers. The highest level of SOD expression was observed in the endosperm at the cherry and over-ripe stages; in addition, these seeds presented the greatest physiological quality (assessed via germination test). The highest CAT3 transcript expression was observed at the green stage in whole seeds, and at the green and over-ripe stages in the embryos and endosperms. High expression of the PPO transcript was observed at the green and yellowish-green stages in whole seeds. In embryos and endosperms, peak expression of the PPO transcript was observed at the green stage; subsequently, peaks at the cherry and over-ripe stages were observed. We concluded that the expression patterns of the SOD and CAT3 transcripts were similar at the more advanced maturation stages, which corresponded to enhanced physiological seed quality. High expression of the PPO transcript at the over-ripe stage, also observed in the embryos and endosperms at the cherry stage, coincided with the highest physiological seed quality.