Virus interference with trans-plasma membrane activity in infected grapevine leaves

The trans-plasma membrane behavior in virus-infected grapevine leaves was investigated and the effects of six viruses included in European and Italian certification protocols of grapevine on trans-plasma membrane potential (t-PMEP) or electron transport (t-PMET) activity were evaluated. Electrophysiological tests were carried out on leaf samples of virus-infected Vitis vinifera cv. Sangiovese. Microelectrodes were placed in the central zone of the mesophyll for membrane potential measurement, while carbon fiber microelectrodes were used to estimate the membrane reductase activity of virus-infected resting cells. Viruses, the presence of which increased the NADH content, interfere differently with t-PMEP and t-PMET. Those that did not interfere negatively with membrane potential caused an increment in cell reductase activity, while virus-infected samples which showed a stressed status-as suggested by low energy availability and difficulty in the impalement procedure-were characterized by a lower t-PMET activity despite NADH content.