Identification and molecular cloning of two homologues of protein phosphatase X fromArabidopsis thaliana

✍ Scribed by Encarna Pérez-Callejón; Antonio Casamayor; Gemma Pujol; Elisabet Clua; Albert Ferrer; Joaquín Ariño

• Book ID: 104619870
• Publisher: Springer
• Year: 1993
• Tongue: English
• Weight: 901 KB
• Volume: 23
• Category: Article
• ISSN: 0167-4412
• DOI: 10.1007/bf00042351

✦ Synopsis

In a recent paper [Ariflo et al., Plant Mol Biol 21:475-485 (1993)] we reported the amplification of a DNA fragment (AP-2) from the genome ofArabidopsis thaliana encoding an amino acid sequence corresponding to a Ser/Thr protein phosphatase distantly related to type 2A protein phosphatases. In this paper we report the use of the AP-2 fragment to isolate several cDNA clones from a leaf cDNA library. Two of these (EP124 and EP129) largely overlap and contain the AP-2 sequence, whereas a third clone (EP128) is different although very related in sequence (86~o of identity). Clones EP124/EP129 and EP128 were found to encode two highly related polypeptides (93 ~o identity) of 305 residues, showing a very high identity (83 ~o) to the catalytic subunit of protein phosphatase X (PPX) from rabbit. Therefore, they have been named PPX-1 (EP124/EP129) and PPX-2 (EP128). Southern blot analysis of genomic DNA indicates that only these two genes encoding phosphatases closely related to PPX are present in the genome ofA. thaliana. Both PPX-1 and PPX-2 are expressed at very low levels in A. thaliana flowers, leaves, stems and roots. The expression levels of four previously identified type 2A phosphatases are higher than those of PPX genes. PP2A-1 appears to be the major mRNA species detected in all the tissues analyzed.