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|Title:||Regulation of Glucanohydrolases in Nicotiana Tabacum on the Messenger-Rnalevel (beta-1,3-Glucanase, Chitinase, Cytokinin, Auxin, Complementary-Dna Clone)|
|Author(s):||Mohnen, Debra Ann|
|Department / Program:||Plant Biology|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Abstract:||Accumulation of the abundant enzymes (beta)-1,3-glucanase and chitinase in cultured tobacco (Nicotiana tabacum L. cv. Havana 425) tissues is inhibited by the hormones auxin and cytokinin. As judged by immunosorption and partial proteolysis of the in vitro translation products, poly(A)+ RNA from tobacco tissues grown on hormone-free medium contains mRNA for a ca. 37kd precursor of the mature 33-34kd (beta)-1,3-glucanase and a ca. 34kd precursor for the mature 32-34kd chitinases.
cDNA clones for glucanase and chitinase were isolated from a cDNA library produced from poly(A)+ RNA from tobacco tissues grown on hormone-free medium. The clones were identified by hybrid-selected translation of the precursor forms of glucanase and chitinase. The largest cDNA clones for each enzyme, ca. 1.0kb in size, were used to study the glucanase and chitinase mRNA accumulation in cultured tobacco tissues.
By Northern analysis a ca. 1.6kb glucanase mRNA and ca. 1.3kb chitinase mRNA were identified in cultured tissues. The kinetics of accumulation of these mRNAs in cultured tobacco tissues were analyzed by Northern and dot blot analysis of total RNA isolated from tobacco tissues treated with auxin and cytokinin. The levels of (beta)-1,3-glucanase and chitinase mRNA increase by up to 20 fold over a 7 day period in tissues subcultured on hormone-free medium or medium containing auxin or cytokinin added separately. Over the same interval of time, the content of glucanase and chitinase mRNA remains at a constant low level in tissues subcultured on medium containing both auxin and cytokinin. These results show that auxin and cytokinin block (beta)-1,3-glucanase and chitinase production at the level of mRNA.
The glucanase and chitinase mRNA content in the intact plant was analyzed by Northern analysis. Lower leaves of 3 to 4 month old plants accumulated levels of glucanase and chitinase mRNA comparable to the highest levels found in cultured tissue while upper leaves contain little or no mRNA for these enzymes. Roots contain levels intermediate between lower and upper leaves. The mRNA and enzyme accumulation patterns were similar.
These results show that hormonal regulation of glucanase and chitinase production in cultured tissues is at the mRNA level and strongly suggest that glucanase and chitinase are under co-regulation both in cultured tobacco tissues and in the plant.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-16|