ALDEHYDE DEHYDROGENASE IN TOBACCO POLLEN

Acetaldehyde is one of the intermediate products of ethanolic fermenta tion, which can be reduced to ethanol by alcohol dehydrogenase (ADH). Alternatively, acetaldehyde can be oxidized to acetate by aldehyde deh ydrogenase (ALDH) and subsequently converted to acetyl-CoA by acetyl-C oA synthetase (ACS). To study the expression of ALDHs in plants we iso lated and characterized a cDNA coding for a putative mitochondrial ALD H (TobAldh2A) in Nicotiana tabacum. TobALDH2A shows 54-60% identity at the amino acid level with other ALDHs and shows 76% identity with mai ze Rf2, a gene involved in restoration of male fertility in cms-T maiz e. TobAldh2A transcripts and protein were present at high levels in th e male and female reproductive tissues. Expression in vegetative tissu es was much lower and no induction by anaerobic incubation was observe d. This suggests that TobALDH expression is not part of the anaerobic response, but may have another function. The use of specific inhibitor s of ALDH and the pyruvate dehydrogenase (PDH) complex indicates that ALDH activity is important for pollen tube growth, and thus may have a function in biosynthesis or energy production.