Characterization of XET-Related Genes of Rice

Abstract

To elucidate the mechanism of internodal elongation in rice (Oryza sativa L.), we analyzed genes encoding xyloglucan endotransglycosylase (XET), a cell wall-loosening enzyme essential for cell elongation. Four rice XET-related (XTR) genes, OsXTR1, OsXTR2, OsXTR3, and OsXTR4, were isolated and their expression patterns in rice plants determined. The expression of the four XTR genes showed different patterns of organ specificity and responses to several plant hormones. OsXTR1 and OsXTR3 were up-regulated by gibberellin and brassinosteroids, whereas OsXTR2 and OsXTR4 showed no clear response to these hormones. Expression of the four XTR genes was also investigated in elongating internodes at different developmental stages. OsXTR1 and OsXTR3 were preferentially expressed in the elongating zone of internodes, while OsXTR2 and OsXTR4 were expressed in nodes and in the divisional and elongating zones of internodes. In three genetic mutants with abnormal heights, the expression of OsXTR1 and OsXTR3 correlated with the height of the mutants, whereas no such correlation was observed for OsXTR2 and OsXTR4. Based on these observations, we discuss the roles that OsXTR1 and OsXTR3 may play in internodal elongation in rice.

Xyloglucan Endotransglycosylases Have a Function during the Formation of Secondary Cell Walls of Vascular Tissues

“…In accordance with its role in the construction and modification of cell wall architecture, XET activity and expression have been detected commonly in growing tissues (Fry et al, 1992;Pritchard et al, 1993;Palmer and Davies, 1996;Burstin, 2000;Uozu et al, 2000;Vissenberg et al, 2000Vissenberg et al, , 2001. In addition, XET also is clearly present in tissues in which expansion has ceased (Arrowsmith and de Silva, 1995;Xu et al, 1995;Palmer and Davies, 1996;Shimizu et al, 1997;Akamatsu et al, 1999;Burstin, 2000;Catalá et al, 2001;O'Donoghue et al, 2001).…”

Constitutive expression of abiotic stress‐inducible hot pepper CaXTH3, which encodes a xyloglucan endotransglucosylase/hydrolase homolog, improves drought and salt tolerance in transgenic Arabidopsis plants

“…A wealth of evidence has been documented that high XTH enzyme activity and its mRNA level were closely correlated with the elongation zone of stems and roots and in ripening fruits in various plant species [23,26,27,[33][34][35][36][37][38]. Analysis of tobacco plants transformed with an antisense construction of NtXET-1 suggested that the reduction in Nt-XET-1 expression might be coupled with strengthening of cell walls [28].…”

“…Table 1 Primer sequences used in the RT-PCR analysis Gene name Accession Number Primer sequence [23,24], potato (xth1) (Genbank Accession No. CAJ77496), Arabidopsis (At-XTH15 and At-XTH22) [25], rice (OsXET_C) [26,27] and tobacco (NtXET_C) [28]. Amino-acid residues that are conserved in at least seven of the ten sequences are shaded, whereas amino-acids that are identical in all ten proteins are shown in black.…”

“…CAJ77496), tobacco (NtXET_C, 46-47%) [28] and monocot rice (OsXET_C, 61-62%) [26,27] plants (Fig. 1B and C).…”

Rice leaf inclination2, a VIN3-like protein, regulates leaf angle through modulating cell division of the collar

“…However, H4, H3 (two molecular markers for the S phase [36]), and EXPB6 (a member of the β-expansin gene family critical for cell elongation in deep water rice [37]) expressions were not obviously altered in the lc2-1 mutant ( Figure 6A, bottom panel). Analysis of the expression of cell-elongation-related genes including XTR1 (encoding xyloglucan endotransglycosylase, the cell-wall loosening enzyme necessary for cell elongation [38]) showed that XTR1 expression was enhanced in the mutant ( Figure 6A, upper panel). Collectively, the results of our study suggest that LC2 mainly regulates cell division through suppressing the expression of cell-division-related genes.…”