| Budget Amount *help |
¥3,930,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥330,000)
Fiscal Year 2007: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2006: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
Intercellular attachment is an essential process in the morphogenesis of multicellular organisms. Pectin is mainly localized in the primary cell wall, middle lamella and cell corners, and is involved in intercellular attachment. Compared with cellulose and hemicellulose, little is known about the biosynthesis and assembly of pectins in cell walls. We have established a novel system for producing mutants by T-DNA transformation called nolac (non) organogenic callus with loosely attached cells), which involves in vitro cultures of leaf disks of haploid Nicotiana plumbaginifolia (Planta 2001) . These mutants are defective in intercellular attachment, which results in the failure of organogenesis. Haploid N. plumbaginifolia plants are suitable for generating and studying cell wall mutants, because mutations have a direct effect on phenotype and because cells with embryo-lethal mutations can be maintained in tissue culture as unorganized callus, which enables us to analyze mutant cell walls
… More
. A novel mutant, nolac-H18 lost the ability to form tight intercellular attachments and adventitious shoots. The gene tagged with T-DNA, named NpGUT1 (glucuronyltransferase 1), was similar to the gene for the catalytic domains of animal glucuronyltransferases and was predominantly expressed in shoot and root apical meristems. The transformation of NpGUT1 complemented the nolac-H18 mutation and the expression of antisense NpGUT1 RNA produced crumbled shoots. The mutation caused defects in the glucuronic acid of rhamnogalacturonan II (RG-II) of pectin, which drastically reduced the formation of borate cross-linking of RG-II. NpGUT1, which encodes a novel glucuronyltransferase, is the first glycosyltransferase gene identified in pectin biosynthesis. It is essential for intercellular attachment in plant meristems and tissues. GUS activity in pNpGUT1:: GUS transgenic tobacco plants was detected in embryo, cotyledon, phloem, tapetum, pollen, pollen tube and transmitting tissue of pistil. The dexamethasone induced expression of the NpGUT1 antisense gene resulted in a significant decrease of NpGUT1 gene expression accompanying with the aberration of pollen, pollen tube and transmitting tissue development in sterile plants. These results indicate that NpGUT1 is required for the formation and function of reproductive tissues. Less
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