Life and death among plant lysophosphatidic acid acyltransferases

The tetraploid Brassica napus possesses several seed-expressed microsomal lysophosphatidic acid acyltransferases (LPAAT ) including BAT1.5, which has been retained after genome duplication as a consequence of a subfunctionalisation of the gene encoding the ubiquitously expressed Kennedy pathway enzyme BAT1.13. Next, cDNA BAT1.3, encoding a LPAAT was subsequently isolated from an embryo library. The rapeseed LPAAT encoded by BAT1.3 is orthologous to the Arabidopsis thaliana At1g51260 gene product possibly associated with tapetum development and male fertility. However, BAT1.3 expression is predominant during the mid stages of embryo development in seeds of Brassica napus. Functional characterisation of BAT1.3 provides further support for a hypothesis of gene dosage sensitivity of LPAATs as does an analysis of the chromosomal localisation of LPAAT genes in Arabidopsis thaliana. The pattern of retention or loss of LPAAT genes after polyploidisation or segmental duplication is consistent with a model of balanced gene drive.