| Popis: |
A P4-chitinase genomic sequence was isolated from a bean ( Phaseolus vulgaris ) genomic library using a P4-ch cDNA. The complete sequence of the P4-ch gene was determined. Primer extension analysis allowed the identification of the transcriptional start site located 79 bp upstream of the translational initiation codon. The gene is interrupted by an intervening sequence. In the 5′ upstream region, a TATT box occurs in place of a TATA at position −33, while a typical CAAT box is found at position −33 with respect to the transcription initiation site. Gibberellic acid, heat shock and salicylic acid regulatory responsive sequences were also identified. Transient expression of chimeric genes in tobacco protoplasts indicated that all the elements required for expression of the coding sequences are present within the first 600 bp of P4-ch 5′ flanking DNA. Various stress conditions such as wounding, salicylic acid and NaCl treatments, heat and cold stress have been applied to the plants. Whereas wounding, NaCl treatment and cold stress are ineffective, transcription of P4-mRNAs is induced upon salicylic acid treatment and, suprisingly, in response to heat stress. P4-chitinase is induced during germination and seems to be constitutively expressed in roots of mature plants. |
