Mentation of root hair and slow growth phenotype of Arabidopsis xxt1 xxt2 double mutant with OsXXT1 in ten-day-old seedlings. Representative examples of root hair and growth are shown. (A) Roots hairs of wild type (WT, Columbia-0), Arabidopsis xxt1 xxt2 double mutant, and complemented Arabidopsis xxt1 xxt2 double mutant with 35S::OsXXT1 (35S::OsXXT1). Bars=100 m. (B) Seedlings of wild type (WT, Columbia-0), Arabidopsis xxt1xxt2 double mutant and 35S::OsXXT1. Bars=2 cm. (This figure is available in colour at JXB online.)4154 | Wang et al.divided into two classes (Fig. 4B). Five genes from rice, and five genes from Arabidopsis–AtXXT1 to AtXXT5, which have demonstrated XXT activity–are grouped into class I. Class II contains two Arabidopsis genes (AtGT6 and AtGT7) and two rice genes (OsGT6 and OsGT7), which are clustered with the fenugreek -(1,6) galactosyltransferase (CAB52246). Although there are 8, 10, and 18 RNA variants encoding GT34 protein members in Arabidopsis, rice, and maize (Penning et al., 2009), respectively, only class I proteins contained both the transmembrane and glycosyltransferase domains in Arabidopsis and rice (Fig. S3, and Fig. 4B). respectively. This suggests that OsXXT1 functions as an XXT gene in rice, as AtXXT1 and AtXXT2 function in Arabidopsis. To test if OsXXT1 possesses xyloglucan 6-xylosytransferase activity, a functional complementation test of the Arabidopsis xxt1 xxt2 double mutant, which displays a root hair development phenotype (Cavalier et al., 2008), was carried out. Expression of OsXXT1 under the 35S CaMV promoter was measured by reverse-transcription PCR (RT-PCR) in complemented transgenic lines (35S::OsXXT1).Trametinib Two transgenic lines showed a high expression level of OsXXT1 (Fig.ADC-Related Custom Services S4), and in these two lines the short root hair growth was restored (Fig.PMID:23880095 5A). Furthermore, the expression of OsXXT1 also partially complemented the slow growth phenotype of the Arabidopsis xxt1 xxt2 double mutant (Fig. 5B). Thus, OsXXT1 may have xyloglucan 6-xylosytransferase similar to AtXXT1 and AtXXT2. To measure the effect of OsXXT1 on XyG synthesis, cell walls from the leaves of wild type, xxt1 xxt2 double mutant and 35S::OsXXT1-complemented Arabidopsis plants were digested with a XyG-specific endoglucanase (XEG) followed by extraction with 4 M KOH. Xyloglucan oligosaccharides released after XEG digestion were analysed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (Fig. 6B). As previously reported, we could not detect any signature of XyG fragment in the Arabidopsis xxt1 xxt2 mutant (Fig. 6B). In the 35S::OsXXT1-complemented Arabidopsis lines, we detected several XyG oligosaccharides, including normal wild-type levels of XXFG, XLLG, and XLFG, and relatively lower level of XXG, XLG, XXXG, and XXLG compared with wild-type plants (Fig. 6A, B).Functional verification of OsXXT1 by complementation of the Arabidopsis xxt1 xxt2 double mutantThe amino acid sequence of OsXXT1 is 70 and 72 identical to that of AtXXT1 and AtXXT2 in Arabidopsis,Expression pattern of OsXXTExpression patterns of rice XXT subfamily genes were determined by examining expression across development using publically available microarray datasets. The expression data are colour coded according to the RNA expression level (Fig. 7). OsXXT1 and OsGT2 have similar expression patterns and are expressed across a variety of tissues. In contrast, other members of this family (OsGT3 to OSGT5) display a more r.