Different expression of ATP-dependent RNA helicases in artificially and naturally induced mango fruitlet abscission

Abstract

Premature fruit drop is a severe production constraint for mango (Mangifera indica) and recent research demonstrates that various physiological parameters and genes are involved in the abscission process. In addition to hormone and carbohydrate responses in the fruitlet, it is evident that ethylene receptors are involved in abscission zone activation. The mango ethylene receptors MiERS1 and MiETR1 respond differently to abscission-inducing ethephon treatments and their expression pattern indicates plant organ specificity. The study regarding the position of those receptors in the mango genome revealed two putative ATP-dependent RNA helicases, which are located upstream of MiERS1. RNA helicases are important for RNA metabolism, post-transcriptional modulation and gene expression. The mango helicase ADRH 7-1 was downregulated in pedicels of fruitlets prone to natural abscission but upregulated in the pedicel abscission zone after ethephon treatment. In contrast, ADRH 7-2 was not responsive to treatments and its transcription level was not significantly changed in the abscission zone. When ethephon-induced fruitlet abscission is compared to naturally induced abscission there are certain differences in the helicase gene expression pattern, as well as in the ethylene receptor expression pattern, while other physiological responses are known to be similar. The presented expression pattern of the ATP-dependent RNA helicase ADRH 7-1 indicates that it might play a role in the transcriptional regulation of the pedicel abscission zone.