MOLECULAR EVOLUTION OF BADH GENES

Abstract

A comparative analysis among 18 Betaine Aldehyde Dehydrogenase (BADH) amino acid sequences was done. BADH enzymes participate in the synthesis of glycinebetaine osmolyte in plant species of economic importance, such as in Chenopodiaceae, Amaranthaceae,
Brassicaceae, Acanthaceae and Poaceae. The molecular evolution of glycinebetaine synthesis pathway and the involved genes, in relation
to regulatory sequences and intracellular localization, were analyzed as a step toward molecular genetic manipulation of the betaine pathway in plants. The amino acid sequence analyses and phylogenetic tree construction were based on sequence alignment obtained with the ClustalX and ClustalW software. The deduced amino acid sequences show that BADH enzymes of dicotyledonous species are
closely related. Dicotyledonous and monocotyledonous BADH enzymes are phylogenetically distant. The homology between two BADHs from amaranth (A. hypochondriacus) was high (98 %), with only 12 amino acid substitutions. This suggests that the evolution of amaranth BADHs constituted relatively recent events. The BADH gene structure and protein coding sequence were conserved during evolution in amaranth (dicotyledonous) and rice (Oryza sativa L.) (monocotyledonous); novertheless, the rice gene contain more small size introns than the amaranth BADH gene. The plant BADH enzymes had significantly different subcellular localization, chloroplasts and peroxisomes.