Expression of a glucomannan mannosyltransferase gene (GMMT) from Aloe vera is induced by water deficit and abscisic acid

Abstract

Highlight 1 GMMT (a possible CSLA9) from Aloe vera is upregulated during water stress. Aloe 2 vera GMMT expression is also induced by exogenous application of the plant 3 stress hormone abscisic acid (ABA) in non-water-stressed plants. 4 5 3 Summary 6 In Aloe barbadensis Miller (Aloe vera), a xerophytic crassulacean acid metabolism 7 (CAM) plant, the main polysaccharide of the gel present in the leaves is an 8 acetylated glucomannan named acemannan. This polysaccharide is responsible 9for the plant succulence, helping it to retain water. In this study we determined 10 using polysaccharide analysis by carbohydrate gel electrophoresis (PACE) that the 11 acemannan is a glucomannan without galactose side branches. We also 12 investigated the expression of the gene responsible for acemannan backbone 13 synthesis, encoding a glucomannan mannosyltransferase (GMMT). It was found 14 by in silico analyses that the GMMT gene belongs to the cellulose synthase like A 15 type-9 (CSLA9) subfamily. Using RT-qPCR it was found that the expression of 16 GMMT increased in Aloe vera plants subjected to water stress. This expression 17 correlates with an increase of endogenous ABA levels, suggesting that the gene 18 expression could be regulated by ABA. To corroborate this hypothesis, exogenous 19 ABA was applied to non-water-stressed plants, increasing the expression of GMMT 20 significantly 48 h after ABA treatment. 21 22