If retinoic acid (RA) is an endogenous regulator of budding, RA synthase should be
active in the developing bud.  RA is produced by oxidation of retinal (retinaldehyde).
This reaction is catalyzed by aldehyde dehydrogenase (ALDH).
   Since many different types of aldehydes are produced in a variety of metabolic
pathways, animals have many different types of ALDHs.  The amino acid sequence
of ALDHs is highly similar to one another so that substrates can hardly be
predicted by the sequence.  We therefore tried to isolate ALDH cDNAs of which
mRNA expression was activated during bud development.
   The figure shows the result of reverse transctiption-polymerase chain reaction
(RT-PCR) analysis of three ALDHs.  The amount of aldh-9 mRNA remained constant
during bud development, suggesting that this ALDH is involved in the house-keeping
activities. The amount of aldh-P7 gradually increased during bud development.
aldh-P18 mRNA was not detected in the adult and the bud at the early stages.
The mRNA was strongly expressed in the 36 hour bud.  The next aim is to examine
whether these ALDHs can synthesize RA
 

Lane 1, adult;  lane 2, 12 h-bud;  lane 3, 24 h-bud;  lane 4, 36 h-bud
 

References

Kawamura,K., Hara,K. & Fujiwara,S. (1993) Developmental role of
     endogenous retinoids in the determination of morphallactic field in
     budding tunicates. Development 117: 835-845.
Harafuji, N., Miyashita, S., Kawamura, K. & Fujiwara, S. (1996) Molecular cloning
   and expression of aldehyde dehydrogenases in the budding ascidian
   Polyandrocarpa misakiensis. Mem. Fac. Sci. Kochi Univ. (Ser. D) 16/17: 7-16.

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