The In Vitro Expression Of Apple PGIP Gene And The Induction Of SA On The Expression Of Peach PGIP Gene

Polygalacturonase inhibiting proteins (PGIPs) are extracellular proteins located in plant cell wall in the defense against plant pathogenic fungus which specifically bind with fungal polygalacturonases and inhibit the activity of polygalacturonase (PGs), activating plant defense responses. Study on PGIP genes and their expression is important for PGIP gene-based plant disease resisitance and cultivar breeding.The full-length cDNA of PGIP gene was cloned from apple fruit, expression vectors for prokaryotic cells and yeast were constructed named as pET-32a-PGIP and pPICZαB-PGIP respectively. Aimed to discover the expression variation of PGIP gene induced by SA spray during fruit development, the real-time PCR was empoyeed to measure the gene expression; main results were as follows:1 The fragment of apple PGIP gene was amplified by reverse transcription polymerase chain reaction with the template of the extracted total RNA from apple fruit. The results showed that the inserted cDNA was 1177 bp in length, containing a full open reading frame of 993 bp encoding 330 amio acids. Expression vectors for prokaryotic cells and yeast were constructed named as pET-32a-PGIP and pPICZαB-PGIP respectively and prokaryotic expression was carried out.2 The result showed that the expression level of PGIP gene in peach leaves and peel were represented by single-peak curves during fruit development. The PGIP gene expression showed a big difference at different developmental stage. The expression peak in peach leaves occurred at fruit-set period while in peel appeared at fruit-rapid expanding period, gene expression highly related to developmental stages. The expression level of PGIP gene in peach leaves was higher than in peel which showed its expression had organ specificity. 0.2,0.02 mmol/L SA induction both had influence on the expression of PGIP gene in peach leaves after 0~72 h,0~24 d treatment, the expression peaks of PGIP gene in peach leaves appeared 24 h and 48 h respectively after 0~72 h SA treatment, the lower concentration SA treatment needed more time to reach peak and had a higher peak value. The expression peak of PGIP gene in peach leaves both appeared 9 d after various concentrations SA treatment in 0~24 d and the lower concentration SA had a higher peak. The long-term effects of SA induction on expression of PGIP gene in peach leaves were relative weak than short-term effects. The expression peak of PGIP gene in peach peel by both SA treatment were lower than the control, which showed SA induction inhibited the expression of PGIP gene in peel.