RT Journal Article
SR Electronic
T1 <em>LAP6/POLYKETIDE SYNTHASE A</em> and <em>LAP5/POLYKETIDE SYNTHASE B</em> Encode Hydroxyalkyl α-Pyrone Synthases Required for Pollen Development and Sporopollenin Biosynthesis in <em>Arabidopsis thaliana</em>
JF The Plant Cell
JO Plant Cell
FD American Society of Plant Biologists
SP 4045
OP 4066
DO 10.1105/tpc.110.080028
VO 22
IS 12
A1 Kim, Sung Soo
A1 Grienenberger, Etienne
A1 Lallemand, Benjamin
A1 Colpitts, Che C.
A1 Kim, Sun Young
A1 Souza, Clarice de Azevedo
A1 Geoffroy, Pierrette
A1 Heintz, Dimitri
A1 Krahn, Daniel
A1 Kaiser, Markus
A1 Kombrink, Erich
A1 Heitz, Thierry
A1 Suh, Dae-Yeon
A1 Legrand, Michel
A1 Douglas, Carl J.
YR 2010
UL http://www.plantcell.org/content/22/12/4045.abstract
AB Plant type III polyketide synthases (PKSs) catalyze the condensation of malonyl-CoA units with various CoA ester starter molecules to generate a diverse array of natural products. The fatty acyl-CoA esters synthesized by Arabidopsis thaliana ACYL-COA SYNTHETASE5 (ACOS5) are key intermediates in the biosynthesis of sporopollenin, the major constituent of exine in the outer pollen wall. By coexpression analysis, we identified two Arabidopsis PKS genes, POLYKETIDE SYNTHASE A (PKSA) and PKSB (also known as LAP6 and LAP5, respectively) that are tightly coexpressed with ACOS5. Recombinant PKSA and PKSB proteins generated tri-and tetraketide α-pyrone compounds in vitro from a broad range of potential ACOS5-generated fatty acyl-CoA starter substrates by condensation with malonyl-CoA. Furthermore, substrate preference profile and kinetic analyses strongly suggested that in planta substrates for both enzymes are midchain- and ω-hydroxylated fatty acyl-CoAs (e.g., 12-hydroxyoctadecanoyl-CoA and 16-hydroxyhexadecanoyl-CoA), which are the products of sequential actions of anther-specific fatty acid hydroxylases and acyl-CoA synthetase. PKSA and PKSB are specifically and transiently expressed in tapetal cells during microspore development in Arabidopsis anthers. Mutants compromised in expression of the PKS genes displayed pollen exine layer defects, and a double pksa pksb mutant was completely male sterile, with no apparent exine. These results show that hydroxylated α-pyrone polyketide compounds generated by the sequential action of ACOS5 and PKSA/B are potential and previously unknown sporopollenin precursors.