Division of roles among members of the XTH gene family in plants

Abstract

The xyloglucan endotransglucosylase/hydrolase (XTH) gene family encodes a class of enzymes responsible for the hydrolysis and/or molecular grafting of xyloglucan, and is considered essential for the construction and restructuring of the cellulose – xyloglucan framework of plant cell walls. Expression analyses of individual XTH gene transcripts in plants, particularly in Arabidopsis and rice, show that most members of this gene family exhibit distinct expression profiles in terms of organ specificity and responses to hormonal signals. Further expression analyses using transgenic plants carrying various XTH promoter::GUS fusion genes have disclosed strict and specific cell-type-dependent expression patterns within respective organs. This implies that each member of this gene family is individually responsible for a specific process regulated by a specific set of signals in a specific tissue at a specific stage of development. By applying this gene expression model to other gene families required for cell wall dynamics, a cell wall-type specific enzyme-set hypothesis has been proposed. This hypothesis suggests that individual cell wall-types are formed and maintained by the concerted action of sets of proteins that consist of selected members from several dozen gene families that are involved in the formation of cell walls. This hypothesis also holds that there is a master gene(s) that defines cell wall-type, and thereby conducts individual enzymes, within a set of proteins, to construct a certain type of cell wall.

Keywords:

• Arabidopsis
• azuki bean
• cell wall
• gene family
• rice
• XTH

Acknowledgements

Supported by a Grant-in-Aid for Scientific Research on Priority Areas (15031202) and Scientific Research (B) (15370016) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and by the Program for “Development of Fundamental Technologies for Controlling the Process of Material Production of Plants” from New Energy and Industrial Technology Development Organization, Japan.

Notes

Abbreviations: ORF, open reading frame; XTH, xyloglucan endotransglucosylase/hydrolase.

Additional information

Notes on contributors

K Nishitani

Abbreviations: ORF, open reading frame; XTH, xyloglucan endotransglucosylase/hydrolase.