Cystatins may confer viral resistance in plants by inhibition of a virus-induced cell death phenomenon in which cysteine proteinases are active: cloning and molecular characterization of a cDNA encoding cysteine-proteinase inhibitor (celostatin) from Celosia cristata (crested cock's comb)

• Published in: Biotechnology and applied biochemistry 2005-12, Vol.42 (3), p.197-204
• Main Authors: Gholizadeh, Ashraf, Santha, Ittiaparambu Mana, Kohnehrouz, Bahram Baghban, Lodha, Madan Lal, Kapoor, Harish Chander
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; antiviral; Base Sequence; Biological and medical sciences; Biotechnology; cell death; Cell Death - drug effects; Celosia; Celosia - chemistry; Celosia cristata; celostatin; Cloning, Molecular; Codon, Initiator; Codon, Terminator; Consensus Sequence; Conserved Sequence; cystatin; Cystatins - genetics; Cystatins - isolation & purification; Cystatins - pharmacology; Cysteine Proteinase Inhibitors - chemistry; Cysteine Proteinase Inhibitors - genetics; Cysteine Proteinase Inhibitors - isolation & purification; Cysteine Proteinase Inhibitors - metabolism; DNA, Complementary - chemistry; DNA, Complementary - genetics; Escherichia coli; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Gene Library; Molecular Sequence Data; Nicotiana - genetics; Nicotiana - virology; Nicotiana glutinosa; Open Reading Frames; Papain - antagonists & inhibitors; Plant Extracts - pharmacology; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - metabolism; tobacco mosaic virus (TMV)
• ISSN: 0885-4513; 1470-8744
• DOI: 10.1042/BA20050029

Cystatins (cysteine proteinase inhibitors) have been recently used in plants as antiviral strategy against those viruses whose replication involves cysteine proteinase activity. We proposed an idea that cystatins may confer resistance by inhibition of a virus‐induced cell‐death phenomenon in which cysteine proteinases are active. To test this idea, a full‐length cDNA library was constructed from the preflowering stage of Celosia cristata (crested cock's comb) leaves, and a cDNA clone with cystatin domain was isolated using an oligonucleotide probe designed on the basis of the conserved peptide of plant cystatins. It was expressed in an Escherichia coli expression system as a fusion protein. The purified recombinant product, termed ‘celostatin’ (Celosia cystatin), inhibited the enzymatic activity of papain indicating its cystatin activity and prevented TMV (tobacco mosaic virus)‐induced hypersensitive‐response cell death in Nicotiana glutinosa (a wild species of tobacco) leaves by 65–70% at the concentration of approx. 50 ng/ml. It also offered resistance against TMV and caused normal growth of the test plant. Since the activity of cysteine proteinases is not involved in the TMV replication process, we speculated that inhibition of the hypersensitive response by celostatin may be due to the inactivation of proteolysis involved in the plant cell death programme, a phenomenon that has already been reported in animal systems.