Molecular cloning of a BcPGIP cDNA from Brassica campestris and its expression to several stresses

Polygalacturonase-inhibiting proteins (PGIPs) play a prominent role as a first line host defense by preventing the polygalacturonases (PGs) activities of the pathogens. Even though PGIPs are regarded as a defensive protein family in plants the expressions of PGIPs are also versatile. Little information is available about the expression of PGIPs to the abiotic stresses. To investigate in response to abiotic stresses we have cloned a cDNA encoding polygalacturonase inhibitory protein (PGIP) by screening a Brassica campestris var. pekinensis (Chinese cabbage) cDNA library. The cDNA of BcPGIP revealed a 999-base pair (bp) open reading frame (ORF) that encoded a protein of 332 amino acids having 10 leucine-rich repeats (LRRs). A 9-bp 5′-untranslated region (UTR) and a 138-bp 3′-UTR were also contained in the ORF of the BcPGIP cDNA obtained. An estimated molecular mass of the cloned BcPGIP was 37.48 kDa and it had an isoelectric point (pI) of 9.26. The putative amino acid sequence of the BcPGIP showed 50-75% similarity to the extracellular PGIPs of other plants. Accumulation of the BcPGIP mRNA was observed in the cotyledons and to a lesser extent, it was also found in the primary roots and in 4-week-old stems while other tissues examined did not show any expression at the mRNA level. Mature leaves, however, had accumulated the transcripts of the BcPGIP gene by the treatment of jasmonic acid. Transcripts of the BcPGIP gene were also observed in the leaves under cold, salt or waterlogged conditions. As the BcPGIP gene was expressed not by salicylic acid but by jasmonic acid and it was also expressed by mechanical wounding as well as by other environmental stresses, it could be speculated that the BcPGIP gene was regulated via jasmonic acid dependent signaling pathway. The results suggest that BcPGIP may involve in plant response to different abiotic stresses.