Effects of Penicillium infection on the expression and activity of CDPK2 in postharvest Hami melon treated with calcium chloride

摘要

Calcium ions are second messengers in plant signal transduction involved in plant growth and development and the response to stress. Calcium-dependent protein kinase (CDPK) is calcium ion receptor functioning in plant disease resistance. Herein, we investigated changes in CDPK activity and resistance to Penicillium in postharvest Hami melons after different treatments. The non-infection group was permeated with calcium chloride (CaCl2) solution, while the infection group was permeated with CaCl2 solution and infected with Penicillium. CDPK activity was elevated in both groups but was higher in the infection group. Analysis of the molecular mechanism of CPDK in Penicillium infection revealed the 1635-bp HmCDPK2 gene with an open reading frame of 1239 nucleotides, encoding a protein of 412 amino acids with a molecular weight of 46161.61 Da and a theoretical isoelectric point of 5.00. The HmCDPK2 protein shares 40.11% tertiary structure similarity with CDPK from the apicomplexan parasite Plasmodium Bergheii (PDB ID 3Q5I). Fluorescence quantitative PCR results showed that expression of HmCDPK2 was upregulated in the infection group relative to the non-infection group, peaking at 12 h after treatment. We conclude that Hami melon develops resistance to Penicillium infection by regulating CDPK activity and upregulating HmCDPK2 expression.