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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)
Author(s) -
Gholizadeh Ashraf,
Santha Ittiaparambu Mana,
Kohnehrouz Bahram Baghban,
Lodha Madan Lal,
Kapoor Harish Chander
Publication year - 2005
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1042/ba20050029
Subject(s) - cystatin , biology , complementary dna , tobacco mosaic virus , biochemistry , cysteine proteinase inhibitors , microbiology and biotechnology , molecular cloning , proteolysis , papain , tobamovirus , cysteine , cdna library , cysteine protease , virus , enzyme , cystatin c , virology , programmed cell death , gene , caspase , apoptosis , renal function
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’ ( Celo sia cy statin ), 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.