Characterization of a @entity523 XXXX gene that is down-regulated by auxin in etiolated hypocotyls.

@entity10056 @entity70645 @entity70646 @entity523 @entity15150
The reorganization of the cellulose-xyloglucan matrix is proposed to serve as an important mechanism in the control of strength and extensibility of the plant primary cell wall. One of the key enzymes associated with xyloglucan metabolism is @entity70645 ( @entity70645 ), which catalyzes the endocleavage and religation of xyloglucan molecules. As with other plant species, XETs are encoded by a gene family in @entity523 ( @entity523 cv T5). In a previous study, we demonstrated that the @entity523 @entity70645 gene LeEXT was abundantly expressed in the rapidly expanding region of the etiolated hypocotyl and was induced to higher levels by auxin. Here, we report the identification of a new @entity523 @entity70645 gene, @entity70646 , that shows a different spatial expression and diametrically opposite pattern of auxin regulation from LeEXT. @entity70646 was expressed more abundantly in the mature nonelongating regions of the hypocotyl, and its mRNA abundance decreased dramatically following auxin treatment of etiolated hypocotyl segments. Analysis of the effect of several plant hormones on @entity70646 expression revealed that the inhibition of @entity70646 mRNA accumulation also occurred with cytokinin treatment. @entity70646 mRNA levels increased significantly in hypocotyl segments treated with @entity15150 , but this increase could be prevented by adding auxin or cytokinin to the incubation media. Recombinant @entity70646 protein obtained by heterologous expression in @entity10056 exhibited greater @entity70645 activity against xyloglucan from @entity523 than that from three other species. The opposite patterns of expression and differential auxin regulation of @entity70646 and LeEXT suggest that they encode XETs with distinct roles during plant growth and development.
