POLYGALACTURONASE INVOLVED IN EXPANSION1 Functions in Cell Elongation and
Flower Development in Arabidopsis |
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Authors: | Chaowen Xiao Chris Somerville Charles T Anderson |
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Institution: | aDepartment of Biology, Pennsylvania State University, University Park, Pennsylvania 16802;bCenter for Lignocellulose Structure and Formation, Pennsylvania State University, University Park, Pennsylvania 16802;cEnergy Biosciences Institute, University of California, Berkeley, California 94704;dDepartment of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720 |
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Abstract: | Pectins are acidic carbohydrates that comprise a significant fraction of the primary
walls of eudicotyledonous plant cells. They influence wall porosity and
extensibility, thus controlling cell and organ growth during plant development. The
regulated degradation of pectins is required for many cell separation events in
plants, but the role of pectin degradation in cell expansion is poorly defined. Using
an activation tag screen designed to isolate genes involved in wall expansion, we
identified a gene encoding a putative polygalacturonase that, when overexpressed,
resulted in enhanced hypocotyl elongation in etiolated Arabidopsis
thaliana seedlings. We named this gene POLYGALACTURONASE INVOLVED
IN EXPANSION1 (PGX1). Plants lacking
PGX1 display reduced hypocotyl elongation that is complemented by
transgenic PGX1 expression. PGX1 is expressed in
expanding tissues throughout development, including seedlings, roots, leaves, and
flowers. PGX1-GFP (green fluorescent protein) localizes to the apoplast, and
heterologously expressed PGX1 displays in vitro polygalacturonase activity,
supporting a function for this protein in apoplastic pectin degradation. Plants
either overexpressing or lacking PGX1 display alterations in total
polygalacturonase activity, pectin molecular mass, and wall composition and also
display higher proportions of flowers with extra petals, suggesting PGX1’s
involvement in floral organ patterning. These results reveal new roles for
polygalacturonases in plant development. |
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