Sequence, identification and characterization of cDNAs encoding two different members of the 18 kDa heat shock family of Zea mays L.

Abstract

Heat-shocked maize seedlings (cv. Oh43) synthesize a characteristic set of heat-shock proteins (hsps) which include an 18 kDa family containing at least six major isoelectric variants. A cDNA library was constructed from poly(A)+ RNAs isolated from the radicles of heat-shocked maize seedlings and screened with a DNA fragment from the theoretical open reading frame of a putative Black Mexican Sweet maize hsp18 genomic clone. Two clones, cMHSP18-3 and cMHSP18-9, were isolated, and the RNA transcripts generated from them were translated into proteins which immunoreact with antibodies directed against the maize 18 kDa hsps and exhibit the same electrophoretic characteristics as two different members of the 18 kDa hsp family. Nucleotide sequence analyses of the cDNAs in these clones reveal that their 5' and 3' untranslated regions exhibit 33-34% identity and that their protein encoding regions share 93% identity. The deduced amino acid sequences of these clones show 90% identity, and the apparent molecular masses and isoelectric points of these proteins agree with those established for two different 18 kDa hsps, numbered 3 and 6. This report substantiates that at least two of the 18 kDa hsps in maize are products of different but related genes. Moreover, it establishes that transcripts for these proteins accumulate during heat shock and that both their nucleotide and deduced amino acid sequences share extensive similarities with the class VI small hsps in soybean and with transcripts expressed during meiosis in Lilium.

The independent stage‐specific expression of the 18‐kDa heat shock protein genes during microsporogenesis in Zea mays L

“…Unlike animal hsps, the majority of hsps synthesized in plants appear to consist of a complex group of low molecular weight proteins with M, of 15,000-30,000 Raschke et al, 19881. Although the size and complexity of the low molecular weight hsps vary among plant species, proteins of approximately 18 kDa comprise the most prominent hsp class in maize [Atkinson et al, 1989;Baszczynski et al, 1982;Goping et al, 19911 and, much like their counterparts in other organisms [Lindquist, 1986;Southgate, 19851, are considered to be encoded from a multigene family.…”

Expression of a Conserved Family of Cytoplasmic Low Molecular Weight Heat Shock Proteins during Heat Stress and Recovery

“…Three of these families have been described from more than one plant species; two families, class I and II, encode proteins that are primarily localized in the cytoplasm and the third encodes chloroplast-localized LMW HSPs. Class I HSPs have been cloned and sequenced from wheat (19), soybean (20) Arabidopsis thaliana (10), and class II cytoplasmic LMW HSPs have been identified in pea (15), soybean (25), and maize (8). Chloroplast LMW HSPs have been sequenced in soybean (28), pea (29), maize (24), petunia (4), and A. thaliana (4).…”

Characterization, chromosomal mapping, and expression of different ubiquitin fusion protein genes in tissues from control and heat-shocked maize seedlings

“…The DNA fragments used as hybridization probes included a DNA fragment from MubG7-1, which contains both the ubiquitin and fusion protein sequences (MubG7-1-2), and a DNA fragment specific for the fusion protein sequence of both MubG7-1 and MubG10-1 (MubG7-1-3). Other DNA probes used in this report for Northern-and dot-blot hybridizations include DNA fragments specific for each of three different maize polyubiquitin genes (MubG1, MubG5, and MubG9) as described in Liu et al (1995), a 0.471 kb DNA fragment containing two maize ubiquitin coding repeats as described in Liu et al (1995), a 0.342 kb Pst IIBgl 11 DNA fragment from the open reading frame of a maize 18 kDa heat shock protein (HSP) as described in Goping et al (1991), a 9.0 kb Eco R1 DNA fragment from a maize ribosomal genomic sequence as described in McMullen et al (1986), and a 4.0 kb Eco RIJBam HI DNA fragment from a maize HSP70 genomic sequence as described in Shah et al (1985). The DNA inserted fragments were excised with the appropriate enzymes, random prime labelled (BRL Life Technologies) with I X -[~~P ]~C T P (Dupont Canada; specific activity -1 x lo9 cmplmg DNA), and hybridized to the RNA blots as described previously (Liu et al 1995).…”

“…Since we have been investigating the response of maize tissues to heat shock, particularly the expression of the genes encoding the maize small heat shock proteins (Goping et al 1991;Atkinson et al 1989Atkinson et al , 1993Bouchard et al 1993) and maize polyubiquitins (Atkinson et al 1989;Bouchard et al 1993;Liu 1992;Liu et al 1995), we decided to assess the effect of heat shock on the expression of the genes encoding some of the maize ubiquitin fusion proteins. Herein, we characterize the nucleotide sequences of genes encoding two different ubiquitin fusion protein transcripts in a maize inbred (Oh43) and use gene-specific DNA fragments from them to (i) map the chromosomal localization of the maize genes encoding these transcripts and (ii) demonstrate, in tissues of 2-and 5-day-old maize seedlings, the effect(s) of heat shock on the expression of each of these genes.…”