important regulators of plant cellulose synthesis

Open Access
Author:
Lei, Lei
Graduate Program:
Plant Biology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 21, 2015
Committee Members:
  • Ying Gu, Dissertation Advisor
  • Ying Gu, Committee Chair
  • Melissa Rolls, Committee Member
  • William O Hancock, Committee Member
  • Charles T Anderson, Committee Member
  • Teh Hui Kao, Special Member
Keywords:
  • cellulose synthesis
  • primary cell wall
  • cellulose microfibrils
  • cortical microfibrils
  • the alignment hypothesis
  • endoglucanase
Abstract:
Cellulose, the world’s most abundant organic compound, is a carbohydrate, composed of several hundred to many thousands of glucose units. Because of the compact sugar molecules in cellulose, it is both a food source for herbivores and a great candidate for alternative biofuel. Plants are the major producers of cellulose on earth. Understanding how plants make cellulose is of the essence. Plant cellulose synthesis is catalyzed by a group of membrane-bound glycosyltransferases, named Cellulose Synthases (CESAs). Genetic studies have revealed that mutations in CESA genes lead to defective cellulose production in plant cell walls. Through forward genetic screens and CESA-interactive protein screens, several non-CESA genes were identified as important regulators for cellulose synthesis in plants. In this dissertation, three of these are discussed in detail: Cellulose Synthase Interactive 1 (CSI1), Cellulose Synthase Interactive 3 (CSI3), and Glycosyl Hydrolase of Family 9 Class A 1 (GH9A1). CSI1 links CESA and microtubules and is the first characterized CESA-interactive protein shown to play a key role in the regulation of cellulose microfibril patterning. More importantly, CSI1 provides a molecular mechanism that explains a long-standing question in the plant biology field: how the patterning of extracellular cellulose microfibrils and intracellular microtubules are coordinated. A CSI1-like protein, Cellulose Synthase Interactive 3 (CSI3), is similar to CSI1 in a lot of aspects but not only an equivalent of CSI1. CSI3 can regulate cellulose biosynthesis in both a microtubule dependent and microtubule independent manner. GH9A1 is an endoglucanase that is important for cellulose synthesis and regulates the organization of both cellulose microfibrils and microtubules in plants. Hopefully, the knowledge we gained from Arabidopsis research will help us understand how cellulose is synthesized in plants and make a better use of cellulose in the near future.