ABA-Glucosyltransferase Involved In Fruit Ripening

Recently, plant hormone abscisic acid (ABA) is a new target for study the fruit ripening which is a complex physiological and biochemical progress. In Arabidopsis glucosyltransferases could glycosylate ABA and regulate ABA homeostasis. This paper focuses the role of glycosyltransferase in fruit ripening of non-climacteric fruit strawberry and climacteric furit tomato.ABA biosynthetic and metabolic genes FaNCEDl, FaNCED2, and FaCYP707A1have been cloned from strawberry fruit. Analysis of ABA contents and genes expression during fruit ripening, results indicated that change of ABA content consistented with expression level of FaNCED2, both of which have peak on white stage then increase during ripening. Expression level of FaCYP707A1has peak on white stage, then decrease during ripening and has lowest level on red stage. Expression levels of three genes have temporal and spatial specific and down-regulated by NAA.Glucosyltransferase (GT) takes part in ABA glucosylation. This paper focuses on the role of GTs during strawberry and tomato fruit ripening. In strawberry fruit, expression levels of mostly GTs have positive correlation with fruit ripening. Both auxin and ABA can regulate expression of GTs, which usually has opposite influence. Ripening process of FaGTl-or FaGT2-silencing strawberry fruit were interrupted, expression level of anthocyanin metabolic and cell wall degradation related genes were decreased, these suggested that FaGT1and FaGT2maybe involved in strawberry fruit ripening. In tomato fruit, SlUGT75C1, SlUGT73C4, and SlUGT76E1have high expression level during fruit ripening. Expression levels of three genes on pulp were higher than on seed. Auxin and ABA triggered expression of there genes. Ripening of SlUGT75C1-silencing tomato fruit was blocked, in which expression levels of ethylene biosynthesis and carotenoid metabolism related genes were down-regulated. Three glucosyltransferases located in chloroplast. Recombinase S1UGT75C1can catalyze ABA and UDPG to produce ABA-GE in vitro. Km is3.24mM and Vmax is0.06uM/min. The above results indicated that glucosyltransferase maybe involved in fruit ripening by affect ABA.In conclusion, the study demostrated ABA glucosyltranferase involed in fruit ripening of two ripening type fruit, provided new evidence for ABA regulated fruit ripening.