Isolation of a wheat cDNA clone for an abscisic acid-inducible transcript with homology to protein kinases.

Abstract

Increases in the plant hormone abcisic add (ABA) initiate water-stress responses in plants. We Plants must adapt to changing environmental conditions. Drought or extreme temperatures trigger large increases in the plant hormone abscisic acid (ABA) and subsequently induce ABA-responsive genes. Plant mutants lacking the ability to produce or respond to ABA are far less capable of surviving environmental stress (1). The steps in the transduction pathway from ABA increases to stress-responsive gene expression are not known. One possible link in this signal transduction pathway is an ABA-regulated protein kinase. In animals and yeast, protein kinase activity often mediates a cellular adjustment to external stimuli (2), and a similar activity in plants is likely.While many ABA-inducible genes have now been cloned, the function of these genes in adaptation to environmental changes is not yet clear. A number of ABA-responsive genes encode late embryogenesis abundant (LEA) proteins that accumulate in drying seeds and in water-stressed seedlings (3-7). In wheat the LEA proteins include Em (8, 9), dehydrin (RAB) (9, 10), group 3 LEA (11), and group 3 LEA (II) (9). Many of the LEA proteins are hydrophilic and may bind water tightly to function as protectants against desiccation (4). The maize LEA protein RAB-17 has been found to be highly phosphorylated in vivo (12, 13). In vitro experiments show that RAB-17 can be phosphorylated by a maize casein kinase II at a serine-cluster region of the protein (14). Whether phosphorylation affects the cellular function of RAB-17 or other LEA proteins has not been determined. (21), and bean and rice (22). We have employed a similar strategy using the polymerase chain reaction (PCR) and oligonucleotide primers to screen an ABA-treated wheat embryo cDNA library for protein kinase clones. We report here the selection and sequence analysis of a cDNA clonet with sequence homology to serine/threonine-specific protein kinases. The transcript corresponding to the clone is inducible both by dehydration and by ABA. MATERIALS AND METHODS Materials and General Methods. Triticum aestivum cv.Brevor was used in all experiments. For the seed developmental study, seeds were harvested from plants grown at the Washington State University Spillman Agronomy Farm near Pullman, WA. Seeds were harvested at 25 days postanthesis (dpa) (70% moisture), at 33 dpa (57% moisture), and at maturity (6.7% moisture). For the dehydration experiments, seeds were germinated and grown on moist filter paper in a high-humidity chamber at 200C. After 3 days the cover of the chamber was removed and the whole seedlings were allowed to dry under low humidity at 20°C. ABA was extracted and assayed with a monoclonal antibody for (S)-ABA (23).Escherichia coli strains XL1-Blue, BB4, and SURE and interference-resistant helper phage R408 were obtained from Stratagene. The cDNA library was prepared from ABAtreated dormant seed embryos of wheat cv. Brevor treated with S ,uM ABA for 12 hr (9). Unless otherwise indicated, protoco...

Immunological evidence that HMG‐CoA reductase kinase‐A is the cauliflower homologue of the RKIN1 subfamily of plant protein kinases

“…n contrast to the results with the anti-RKIN1 and anti-BI, JN12 sera, the 58 kDa subunit was not recognized (not sh, ,wn) by antipeptide antibodies raised against sequences from ra~ AMPK, S. cerevisiae Snflp, or wheat PKABAl [21]. The lal er is a representative of a subfamily of plant protein kinases wl: ich are also related to Snfl p, albeit somewhat more distantly th, n RKINI/BKINI2 [22].…”

Role of Abscisic Acid in Seed Dormancy

“…Characterization of the protein kinase PKABA1 provides further support for a role of reversible protein phosphorylation in ABA signaling (Anderberg and Walker-Simmons 1992). PKABA1 is an ABA-responsive protein kinase whose synthesis is upregulated in the dormant mature-imbibed cereal grain.…”

Two genes that encode ribosomal‐protein S6 kinase homologs are induced by cold or salinity stress in Arabidopsis thaliana

“…ATPK6 genes under stress conditions Recently, the transcription levels of protein kinases [22][23][24], transcription factors [25,26], G proteins [27], and calmodulins [28] in plants have been reported to be affected by environmental stresses (e.g. light, temperature, mechanical stress, and dessication).…”