A sugarcane cystatin: recombinant expression, purification, and antifungal activity.

Plants possess several defense mechanisms against pathogenic attack. One of these defenses is the use of protease inhibitor proteins, which interfere in the development and growth of pathogens. Sugarcane productivity can be impacted by the plant's susceptibility to fungal diseases that result in production losses. A relevant line of investigation, therefore, is into the plant's natural defense mechanisms for the control of phytopathogens using cystatins-proteins that specifically inhibit cysteine proteases. In this paper, we discuss the expression, in Escherichia coli, of a sugarcane cystatin, its purification, antifungal activity, and circular dichroism to monitor correct folding. These studies revealed a secondary structure similar to that of the oryzacystatin I of rice. Moreover, the purified protein proved capable of inhibiting the growth of the filamentous fungus Trichoderma reesei, suggesting that it can also be employed to inhibit the growth of pathogenic sugarcane fungi.