Cathepsin B cysteine protease gene is upregulated during leaf senescence and exhibits differential expression behavior in response to phytohormones in Picrorhiza kurrooa Royle ex Benth.

• cDNA encoding cathepsin B-like cysteine protease (Pk-cbcp) cloned from Picrorhiza
• Pk-cbcp cDNA consisted of 1369 bp with a 1080 bp ORF, 80 bp 5′ UTR, 209 bp 3′ UTR.
• Abscisic acid and jasmonic acid increased the expression level of Pk-cbcp mRNA.
• Cytokinin reduced the expression level of Pk-cbcp mRNA.
• Pk-cbcp may play a role in leaf senescence.

Medicinal importance of Picrorhiza (Picrorhiza kurrooa Royle ex Benth — an herb of western Himalayan region) and its endangered status in Red Data Book presses an urgent need for intensive R&D interventions towards ensuring its availability for the medicinal use, its sustainability and improvement. The present study was conducted on cathepsin B cysteine protease in Picrorhiza. Cathepsin B cysteine protease has been reported to function in diverse processes such as senescence, abscission, programmed cell death, fruit ripening and in response to pathogen and pest attacks. A full-length cDNA-Pk-cbcp encoding cathepsin B-like cysteine protease was cloned from Picrorhiza. The full length Pk-cbcp cDNA consisted of 1369 bp with an open reading frame of 1080 bp, 80 bp 5′ untranslated region and 209 bp 3′ untranslated region. The deduced Pk-cbcp protein contained 359 amino acids with a molecular weight of 39.981 kDa and an isoelectric point of 5.75. Secondary structure analysis revealed that Pk-cbcp had 28.97% α-helices, 14.48% β-turns, 19.50% extended strands and 37.05% random coils. Semi-quantitative PCR analysis revealed 157% higher expression of Pk-cbcp during senescence compared to that of pre-senescence. Further, application of phytohormones abscisic acid, jasmonic acid and cytokinin influenced the temporal expression status of Pk-cbcp. Abscisic acid and jasmonic acid increased the expression level whereas cytokinin reduced the expression. The findings suggest the role of Pk-cbcp in leaf senescence in Picrorhiza which may be differentially mediated through phytohormones.