Betalains and expression of antioxidant enzymes during development andabiotic stress in Rivina humilis L. berries

Authors: MOHAMMAD IMTIYAJ KHAN, AVINASH KUMAR, PARVATAM GIRIDHAR

Abstract: This work investigated the betalains profile and associated molecular changes during Rivina humilis L. Berry development and 1 month after inducing stress through elicitors such as salicylic acid (SA, 0.05-0.5 mM) and chitosan (CH, 0.1%-1.0%). The results showed that, during berry development, diphenol oxidase activity of tyrosinase increased, which was reflected in an exponential increase in betalains accumulation. Expression levels of a putative Rivina humilis betanidin-5-O-glucosyltransferase 2 (RhBGT2) remained unchanged, while that of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) decreased. Treatment with SA (0.1 mM) and CH (0.5%) enhanced betalains accumulation. The pattern of betalains accumulation during berry development and after elicitor treatment suggested that, probably, both betacyanins and betaxanthins are synthesized from the same pool of betalamic acid. There was no significant change in expression levels of RhBGT2, SOD, and CAT following elicitor stress. However, treatment with CH (1.0%) produced morphological changes (shrinking) in the berries and expression of SOD was significantly suppressed. This is the first report that shows enhancement of betalains accumulation in intact berries through elicitor treatment.

Keywords: Salicylic acid, chitosan, glucosyltransferase, superoxide dismutase, catalase

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