Cloning of cDNAs encoding the three subunits of oxygen evolving complex in Nicotiana benthamiana and gene expression changes in tobacco leaves infected with Tobacco mosaic virus

In this study, the cDNAs encoding 33, 23 and 16 kDa proteins of an oxygen-evolving complex (OEC) in Nicotiana benthamiana and in Nicotiana tabacum (16 kDa only) were cloned using the RT-PCR method. The three proteins were expressed in Escherichia coli and antiserum against these proteins was raised in rabbit. Using the antiserum, the levels of three OEC proteins were investigated and compared in N. benthamiana and N. tabacum plants inoculated with Tobacco mosaic virus (TMV). In leaves of N. tabacum that showed typical mosaic symptoms, the level of the 33 kDa protein had no detectable change (p>0.05p>0.05), while the levels of the 23 and 16 kDa proteins were significantly reduced (p<0.01p<0.01), when compared with the levels in mock-inoculated plants. In leaves of N. benthamiana   that were a smaller size and exhibited the abaxial curling symptom, the levels of all three proteins had no detectable changes (p>0.05p>0.05). These results suggest that the expression profile of OEC proteins may be involved in the symptom types of plants infected with TMV. The decrease of 23 and 16 kDa protein levels may result in the chlorosis of N. tabacum leaves infected with TMV. In addition, this is the first report of the cDNA sequence of the 16 kDa protein in Nicotiana species.