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Oryza sativa chymotrypsin inhibitor-like 2 (OCPI2) is a member of serine PI family[1].

Annotated Information


  • Protease inhibitors play important roles in stress and developmental responses of plants. Rice genome contains 17 putative members in chymotrypsin protease inhibitor (ranging in size from 7.21 to 11.9 kDa) gene family with different predicted localization sites[1].
  • Full-length cDNA encoding for a putative subtilisin–chymotrypsin protease inhibitor (OCPI2) was obtained from Pusa basmati 1 (indica) rice seedlings. 620 bp long OCPI2 cDNA contained 219 bp-long ORF, coding for 72 amino acid-long 7.7 kDa subtilisin–chymotrypsin protease inhibitor (CPI) cytoplasmic protein[1].

GO assignment(s): GO:0004867,GO:0009611


Another CPI gene (OCPI1)[2] upstream to OCPI2 (with 1126 bp distance between the transcription initiation sites of the two genes; transcription in the reverse orientation) was noted in genome sequence of rice genome. A vector that had GFP and GUS reporter genes in opposite orientations driven by 1881 bp intergenic sequence between the OCPI2 and OCPI1[2] (encompassing the region between the translation initiation sites of the two genes) was constructed and shot in onion epidermal cells by particle bombardment[1].


  • Transgenic rice plants[1]:

Transgenic rice plants produced with OCPI2 promoter-gus reporter gene showed that this promoter directs high salt- and ABA-regulated expression of the GUS gene.


  • Amongst different stresses tested, mechanical injury appeared to exert maximum up regulation of both the transcripts in root as well as shoot tissues[1].
  • Expression analysis by semi-quantitative RT-PCR analysis showed that OCPI2 transcript is induced by varied stresses including salt, ABA, low temperature and mechanical injury in both root and shoot tissues of the seedlings[1].
  • Expression of both GFP and GUS from the same epidermal cell showed that this sequence represents a bidirectional promoter. Examples illustrating gene pairs showing co-expression of two divergent neighboring genes sharing a bidirectional promoter have recently been extensively worked out in yeast and human systems[1].


Analysis of the conserved domains of the protein using the NCBI Conserved Domain Search revealed that OCPI2 belongs to the potato inhibitor I family of proteins. Mapping of the transcription initiation site showed that the transcription for the OCPI2 gene starts 138 bp upstream of the translation start site. The comparison of the cDNA sequence with the genomic sequence revealed that a 97 bp intron is present in the 5′ UTR region of this gene[1].

Knowledge Extension

  • Proteinase inhibitors (PI) constitute a large and complex group of plant proteins and have an enormous diversity of function by regulating the proteolytic activity of their target proteinases, resulting in the formation of a stable protease inhibitor complex[2][3].
  • PIs were classified into non-specific and class-specific superfamilies and the later was subcategorized into several families including serine proteinase inhibitor, aspartic proteinase inhibitor, metalloproteinase inhibitor, and cysteine proteinase inhibitor[4]. Genes encoding for PIs have been cloned and characterized from a varied range of plant species[5].
  • Primarily, PIs are considered important in endogenous as well as exogenous defense against various pathogenic organisms[5]. Some insects and many of the phyto-pathogenic microorganisms produce enzymes causing proteolytic digestion of host proteins. Plants fight against these pathogens through PIs that act against the proteolytic enzymes. Also, plant PIs have been shown to be involved in various physiological and developmental responses[2][4].

Labs working on this gene

  • National Center of Plant Gene Research (Wuhan), National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan 430070, China
  • Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi-110021, India


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Singh A, Sahi C, Grover A. Chymotrypsin protease inhibitor gene family in rice: Genomic organization and evidence for the presence of a bidirectional promoter shared between two chymotrypsin protease inhibitor genes[J]. Gene, 2009, 428(1): 9-19.
  2. 2.0 2.1 2.2 2.3 Huang Y, Xiao B, Xiong L. Characterization of a stress responsive proteinase inhibitor gene with positive effect in improving drought resistance in rice[J]. Planta, 2007, 226(1): 73-85.
  3. Leung D, Abbenante G, Fairlie D P. Protease inhibitors: current status and future prospects[J]. Journal of medicinal chemistry, 2000, 43(3): 305-341.
  4. 4.0 4.1 Hibbetts K, Hines B, Williams D. An overview of proteinase inhibitors[J]. Journal of Veterinary Internal Medicine, 1999, 13(4): 302-308.
  5. 5.0 5.1 Habib H, Fazili K M. Plant protease inhibitors: a defense strategy in plants[J]. Biotechnology and Molecular Biology Review, 2007, 2(3): 68-85.

Structured Information