Preparation of a Xyloglucan Oligosaccharide Mixture from Tamarind Seed Gum and its Promotive Action on Flower Opening in Carnation Cultivars

Abstract

A mixture of xyloglucan oligosaccharides (XGO) was prepared from xyloglucan (XG) of tamarind seed gum by digestion with Aspergillus recombinant XG-specific xyloglucanase and subsequent purification by ethanol fractionation. The XGO mixture contained XG7, XG8, and XG9 at the ratio of 1 : 4 : 5, which was almost identical to the literature value of constituent subunits ratio of 1.2 : 3.8 : 5. The XGO mixture at 1% promoted flower opening in carnation (Dianthus caryophyllus L.) cultivars, such as 'Pure Red' and 'Lillian'. On the other hand, there was no effect on other cultivars, such as 'Collin', 'Light Pink Barbara', and 'Mule'. Promotion of flower opening by 1% XGO was exhibited earlier than that by glucose or sucrose at 1% in 'Pure Red' carnation. Separate application of XG7 or XG9 stimulated flower opening in 'Pure Red' carnation, suggesting that all the constituents in the XGO mixture were effective in stimulating flower opening. Based on these observations, the mechanism of action of XGO on carnation flower opening and its future practical use as a flower-opening agent are discussed.

Identification and Characterization of Plasma Membrane Intrinsic Protein (PIP) Aquaporin Genes in Petals of Opening Carnation Flowers

“…Those genes encode enzymes that are involved in petal cell expansion such as xyloglucan endotransglucosylase/hydrolase (XTH), expansin, and sucrose synthase. In addition, xyloglucan oligosaccharides (XGO) treatment was found to promote flower opening in some carnation cultivars including 'Pure Red' in the course of our study on chemical control of flower opening in carnations (Satoh et al, 2013).…”

“…Excluding DcPIP2;4 and DcPIP2;5 with putatively low expression levels estimated by the number of ESTs (1 and 3 ESTs, respectively), the expression of PIP genes was analyzed using petals of opening flowers and green leaves sampled from cut flowers. We used a cultivar 'Pure Red' in this study since the enhancement of flower opening by XGO treatment was prominent in this cultivar in our previous study (Satoh et al, 2013). As a result, DcPIP2;1 and DcPIP1;1 showed high expression levels in both petals and leaves compared with other DcPIPs in 'Pure Red' (Fig.…”

“…In a previous study, we observed that XGO treatment enhanced flower opening in the 'Pure Red' carnation (Satoh et al, 2013). On the assumption that water uptake in petal cells may be associated with the enhancement of flower opening by XGO, we examined the expression of DcPIP2;1 and DcPIP1;1 in XGO-treated flowers.…”

“…The control solution was distilled water, and the test solution contained the XGO mixture at 1% in distilled water. The XGO mixture consisted of XG7 (xyloglucan heptaoligosaccharide), XG8 (xyloglucan octaoligosaccharide), and XG9 (xyloglucan nonaoligosaccharide) at a ratio of 1:4:5 was prepared from tamarind seed gum as described previously (Satoh et al, 2013) stored at −80°C as described above. In this experiment, 6 flowers were treated with XGO, and petals taken from 2 flowers were mixed to make one sample so that three independent samples were collected.…”

“…Our data thus suggest that XGO treatment does not enhance the expression of genes associated with flower opening. XGO may affect flower opening by modulation of cell wall expansion through incorporation of XGO into cell walls by xyloglucan endotransglycosylase activity of XTH, as proposed by Satoh et al (2013), rather than up-regulation of the genes involved in petal growth. In summary, we identified a carnation AQP family by an in silico search and characterized PIP genes expressed in flowers of the 'Pure Red' carnation.…”