Two closely related cDNAs encoding actin-depolymerizing factors of petuniaare mainly expressed in vegetative tissues

Actin-depolymerizing factor (ADF) is one of the small actin-binding protein s that regulate actin dynamics in cells. We have isolated two cDNA clones, PhADF1 and PhADF2, encoding ADF from cDNA libraries constructed from petal protoplast cultures and flowers of Petunia hybrida. PhADF1 and PhADF2 encod e polypeptides of 139 and 143 amino acids with a calculated molecular mass of 16.04 and 16.51 kDa, respectively. Go-sedimentation assay showed that th e recombinant PhADF1 protein produced in Escherichia coli binds to F-actin at pH 7.0 and preferentially depolymerizes it at pH 8.0. Gene tree analysis indicates that the plant ADF family can be grouped into four classes, and PhADFs are included in class I. Southern blot analyses revealed that one or two copies of PhADF genes are present in petunia genome, and several other related isoforms also exist. Northern blot analyses indicated that PhADF1 and PhADF2 are closely related and abundantly expressed in every plant orga n except pollen. In addition, they are highly accumulated in mature vegetat ive tissue (petal, leaf, and stem). Our results indicate that the transcrip tion of petunia ADF genes is differentially regulated by developmental sign als. (C) 2000 Elsevier Science B.V. All rights reserved.