Go to  Advanced Search

Analysis of the Arabidopsis fatty acyl-CoA synthetase5 gene and co-expressed genes reveals an ancient biochemical pathway required for pollen development and sporopollenin biosynthesis

Show full item record

Files in this item

Files Size Format Description   View
ubc_2011_fall_kim_sungsoo.pdf 4.770Mb Adobe Portable Document Format   View/Open
 
Title: Analysis of the Arabidopsis fatty acyl-CoA synthetase5 gene and co-expressed genes reveals an ancient biochemical pathway required for pollen development and sporopollenin biosynthesis
Author: Kim, Sung Soo
Degree Doctor of Philosophy - PhD
Program Botany
Copyright Date: 2011
Publicly Available in cIRcle 2011-06-24
Abstract: The structure of the sporopollenin polymer that is the major constituent of exine, the outer pollen wall, remains poorly understood. In flowering plants, sporopollenin precursors are known to be produced in the tapetum and must be deposited and polymerized on the developing microspore during exine formation. Recent characterization of Arabidopsis thaliana genes and corresponding enzymes involved in exine formation has demonstrated the role of fatty acid derivatives as precursors of sporopollenin building units. In collaboration with other research groups, we discovered that the Arabidopsis ACOS5 gene is transiently and exclusively expressed in tapetum cells and that an Arabidopsis acos5 mutant is completely male sterile with pollen grains that are apparently devoid of sporopollenin. In this thesis, Arabidopsis genes encoding potential enzymes that could work with ACOS5 in a common biosynthetic pathway were identified by in silico co-expression analyses and functionally characterized. Previous studies and my reverse genetic analyses of selected co-expressed genes including POLYKETIDE SYNTHASE A and POLYKETIDE SYNTHASE B (PKSA/B), and TETRAKETIDE α-PYRONE REDUCTASE1 and TETRAKETIDE α-PYRONE REDUCTASE2 (TKPR1/2) revealed that mutants in these genes are also compromised in male fertility and sporopollenin deposition. In vivo biochemical assays by heterologous expression of PKSA in the yeast Saccharomyces cerevisiae showed that the enzyme catalyzes condensation of endogenous fatty acyl-CoAs with malonyl-CoA to generate α-pyrone triketides. Moreover, in vitro assays performed by collaborators revealed that the sequential actions of ACOS5, PKSA/B, and TKPR1/2 enzymes on fatty acid substrates generate polyhydroxylated long-chain α-pyrones, suggesting that these novel coumpounds are building units of sporopollenin. Phylogenetic analyses showed that these genes are highly conserved in land plants including the moss Physcomitrella patens. This work has illuminated the outlines of a conserved novel biosynthetic pathway involved in generating monomer constituents of the sporopollenin biopolymer component of the pollen wall.
URI: http://hdl.handle.net/2429/35743
Scholarly Level: Graduate

This item appears in the following Collection(s)

Show full item record

All items in cIRcle are protected by copyright, with all rights reserved.

UBC Library
1961 East Mall
Vancouver, B.C.
Canada V6T 1Z1
Tel: 604-822-6375
Fax: 604-822-3893