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Abstract
Make the Parallel Lines Meet – Towards A Better Understanding of Cellulose Biosynthesis
Lei Lei
Center for Lignocellulose Structure and Formation, Department of Biochemistry and Molecular Biology, Pennsylvania State
University, University Park, PA 16802
Cellulose, the word’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. And
cellulose itself is a major and load-bearing component of plant cell wall, which serves important roles in
providing rigidity, tensile strength, structural support, and protection against all kinds of stress challenges (biotic
and abiotic) 1, 2. Understanding how plants make cellulose and control the structure of cell wall is of essence. A
long-standing question in the plant biology field is how information is transferred from cortical microtubules to
cellulose microfibrils. At last, we discovered a mechanism to settle the more than fifty-year debate for the
potential linker between microtubules and cellulose synthesizing machinery: Cellulose synthase interactive 1
(CSI1) is a CSC-microtubule linker protein, required for guidance of primary cellulose synthase complexes
(CSCs) along cortical microtubules during cellulose biosynthesis3. In addition to the role of linking CSCs and
microtubules, CSI1 also labels SmaCCs/MASCs4. SmaCCs/MASCs, whose function was not well understood, are
cortical CSC-containing compartments that can be strongly induced under stress conditions5, 6. We proposed a
mechanism that CSI1 is required for fast recycling of CSCs from SmaCCs/MASCs to the plasma membrane 7. The
potential function of SmaCCs/MASCs will also be discussed. Indicated from the phenotype of csi1 mutants, we
also started a forward genetic screening for mutants with relative mild root swollen phenotype, designated jiaoyao
(僬侥). The first characterized jiaoyao1 mutant is a new allele of korrigan1, which has been studied for almost
twenty years but not well understood. jiaoyao1 is a missense allele of KOR1/GH9A1 which has a point mutation
in the catalytic site of KOR1/GH9A1. jiaoyao1 mutation disrupts the endoglucanase activity of KOR1/GH9A1
and regulates the organization of both cellulose microfibrils and microtubules. We proposed that KOR1/GH9A1 is
likely a multi-functional protein in plants. Plant cellulose synthesis is a beautiful process of complexity and
coordination. Hopefully, the knowledge we gained from model plant research will be applicable to help the
human society to keep renewable and sustainable development.
[1] Underwood. (2012) Front. Plant Sci., 3: p85.
[2] Tenhaken. (2014) Front. Plant Sci., 5: p771.
[3] Li et al. (2012) Proc. Natl. Acad. Sci., 109, 185-190.
[4] Lei et al. (2012) Plant Signal. Behav., 7, 714-718.
[5] Gutierrez et al. (2009) Nat. Cell Biol., 11(7), 797-806.
[6] Crowell et al. (2009) Plant Cell, 21(4), 1141-1154.
[7] Lei et al. (2015) Plant Cell, 21(4), 1141-1154.
[8] Lei et al. (2014) Plant Cell, 26(6), 2601-2616.