Differential accumulation of transcripts encoding protein kinase homologs in greening pea seedlings

Abstract

Degenerate oligonucleotides, corresponding to conserved regions within the catalytic domain of known protein-serine/threonine kinases, were used as primers for the polymerase chain reaction to amplify cDNA synthesized from poly(A)+ RNA purified from the apical buds of 7-day-old pea seedlings. Five partial cDNAs were obtained and designated PsPK1 through PsPK5 (for Pisum sativum protein kinase) in order of decreasing length. The deduced amino acid sequences show that each member of the PsPK series is different in length, and, although their sequences are quite similar overall, each has a unique sequence. Moreover, each member of the PsPK series has structural features typical of members of the protein-serine/threonine kinase family of protein kinases. All are equally similar to cyclic nucleotide-dependent protein kinase and protein kinase C, suggesting that the pea homologs may be involved in signal transduction. DNA gel blots show that each PsPK cDNA is likely to be encoded by a single gene within the pea genome. RNA blot analyses show that the PsPK transcripts accumulate differentially during greening of etiolated seedlings. PsPK3 and PsPK5 transcripts show a large and rapid decline during deetiolation. In contrast, the level of PsPK4 RNA increases steadily during deetiolation whereas PsPK1 and PsPK2 transcripts show little change during the greening period. Thus light regulates changes in the levels of transcripts encoding putative protein kinases in plants.