Isolation and characterization of a cDNA clone encoding a novel jasmonate-induced protein of barley (Hordeum vulgare L.).

Abstract

Jasmonic acid and its methyl ester seem to be ubiquitously distributed throughout the plant kingdom [ 1 ]. These compounds have been shown to possess various physiological activities when applied to plants exogenously, including growth inhibition, promotion of leaf senescence, inhibition of seed germination and induction of tuberization in potato [2, 3]. Jasmonate has also been shown to alter gene expression in many plant species [4]. Treatment of barley leaf segments with j asmonate leads to the rapid accumulation of a specific set of proteins, the so-called jasmonateinduced proteins (JIPs [2]) whereas translation of other polypeptides is shut down [5]. Since the induction of the new proteins takes place at the level of mRNA, it has been possible to isolate cDNA clones for two of the major jasmonateinduced proteins from barley leaves by differential screening [6]. One of these cDNAs encodes a barley leaf thionin, which has been considered to be part of a defense mechanism against pathogens [6, 7]. The second cDNA encodes the major jasmonate-induced protein of Mr 23000 [6]. In addition to these two proteins there are several other jasmonate-induced proteins for which sequence information is not yet available. Here we report the nucleotide sequence of another near-fulMength cDNA clone which encodes a novel jasmonate-induced protein of Mr 60000 from barley, cDNAs have been isolated by differential screening representing transcripts which accumulate during dark-induced senescence of detached barley leaves (W. Becker and K. Apel, in preparation). One of these cDNAs (cDNA clone pHvS61) corresponds to a transcript that accumulates also in jasmonate-treated leaf segments to high levels. Since pHvS61 contalned only a short cDNA fragment of 200 bp the insert was used as a probe to screen another cDNA library in 2gtl0 constructed from poly(A)containing RNA of jasmonate-treated barley leaf segments [6]. Among several positive clones the clone pHvJ611 was selected for further studies. The length of the cDNA insert was close to the predicted size of he corresponding transcript deduced from northern blot analysis. The cDNA contained an open reading frame encoding a polypeptide of 60 368 Da. No significant similarity to other protein sequences was found in a data bank search (MIPSX, release 28.0).