Cloning of two plant cDNAs encoding a beta-type proteasome subunit and a transformer-2-like SR-related protein: early induction of the corresponding genes in tobacco cells treated with cryptogein.

We report the successful combination of mRNA differential-display reverse-transcription PCR (DDRT-PCR) and 5'-rapid amplification of cDNA ends (5'-RACE) in order to isolate full-length cDNAs corresponding to genes activated in tobacco cells treated with cryptogein within 60 min. Cloning and sequencing of two cDNAs, called 'tcI 7' and 'tcI 14' (for tobacco cryptogein-induced), allowed the identification of open reading frames. Deduced amino-acid sequences of 'tcI 7' and 'tcI 14' showed significant homologies with a beta-type proteasome subunit and a transformer-2-like serine/arginine-rich (SR) ribonucleoprotein, respectively. The accumulation of mRNAs corresponding to 'tcI 7' started 30 min after the addition of cryptogein to tobacco cell suspensions and continued up to 180 min, whereas the accumulation of 'tcI 14' corresponding mRNAs was transitory between 30 and 60 min. These results indicated a transcriptional activation of the corresponding genes early after elicitation of tobacco cells by cryptogein. The biological significance of this activation remains to be elucidated.