Biosynthesis of Xyloglucan in Grasses and Identification of Endosperm Developmental Phases in Wheat Seeds

 
 
 
 

Biosynthesis of Xyloglucan in Grasses and Identification of Endosperm Developmental Phases in Wheat Seeds

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Title: Biosynthesis of Xyloglucan in Grasses and Identification of Endosperm Developmental Phases in Wheat Seeds
Author: Nadella, Ramya
Description: Xyloglucans are the major hemicellulosic polysaccharides in the primary cell walls of dicots and non-graminaceous monocots but small amounts are also seen in the walls of grasses. They serve as cross-linkers of cellulose microfibrils and maintain the structural integrity of the cell.Xyloglucan biosynthesis mechanism is well understood and many biosynthetic genes have been identified in dicots. However this process is not known in grasses where structural differences in xyloglucan exist. Thus, this study aimed to investigate xyloglucan biosynthesis in grasses by functionally characterizing some xyloglucan biosynthetic genes, particularly the xylosyltransferases from wheat and rice. Wheat (TaGT34-7) and rice (OsGT34-3) homologs of Arabidopsis xyloglucan-xylosyltransferase (AtXT1) gene were previously identified using a bioinformatic script developed by Faik et al. (2006). The full-length cDNAs encoding TaGT34-7 and OsGT34-3 proteins were expressed in Pichia pastoris and Drosophila S2 expression systems, but the proteins did not show xylosyltransferase activity in Pichia pastoris and a low activity in Drosophila S2 cells. Further optimization is required to fully identify the function of these two proteins. In another study, the endosperm developmental phases were identified in developing wheat seeds using sectioning and light microscopy. Cell walls of wheat endosperm have ~70% (w/w) of arabinoxylan (AX), 20% (w/w) of mixed linked glucan (MLG), and only 5% (w/w) of cellulose. MLG and AX are deposited during cellularization and differentiation phases of the endosperm development, respectively. To identify the putative glycosyltransferase genes involved in the biosynthesis of these polymers (AX, MLG), it was necessary to first identify the endosperm developmental phases namely cellularization and differentiation phases at which they are deposited. Fresh wheat seeds were collected and their endosperm developmental phases were investigated using sectioning and light microscopy methods. Also, starch deposition was monitored using polarized light microscopy.
Permanent Link: http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1194976732
http://hdl.handle.net/2374.OX/14616
Date: 2007

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