Sangha, Manjeet KaurBrar, Gundeep Kaur2017-12-032017-12-032017http://krishikosh.egranth.ac.in/handle/1/5810036776Ribosome inactivating proteins (RIPs) are N-glycosydases, which catalyse the depurination of conserved single adenine (A4034) in yeast ribosomal RNA, leading to cell death. They are endowed with antimicrobial activities against bacteria, fungi and viruses in plants and animals. Cotton leaf curl disease (CLCuD) transmitted by whitefly (Bemisia tabaci) affects cotton production in northern India. In the present study, RIPs were purified by ion exchange chromatography (SP and CM sepharose) from the seeds of seven crops viz. Momordica charantia, Momordica balsmina, Spinacia oleracea, Phaseolus vulgaris, Cucurbita moschata, Zea mays and Hordeum vulgare. RIPs purified from M. balsmina and M. charantia showed maximum per cent recovery of 12.8 and 11.06 respectively. They also depicted maximum RIP activity on yeast ribosomal RNA by qualitative depurination assay. Depurination assay was carried out on ribosomes isolated from yeast. Both purified RIPs gave a single homogenous band on PAGE and SDS-PAGE of 28kDa. They registered a pI value of 10 on isoelectric focusing, showing them to be highly basic. Secondary structure determination of balsmina and charantia RIPs by CD spectroscopy revealed the presence of both alpha helices (23.5% and 32.8%) and beta sheets (24.6% and 43.6%). The RIPs also exhibited superoxide dismutase and chitinase activity. The purified balsmin RIP @0.250 mg/ml and charantia RIP @0.250 mg/ml and @0.500 mg/ml were sprayed on two cotton cultivars LH2076 and F1378, before and after whitefly infestation. Disease incidence was recorded after 28 and 40 days of RIP treatment. The disease incidence was found to be lower (20%-60%) in plants sprayed with RIPs as compared to their respective controls (100%). The latency or absence of virus was verified by PCR analysis using coat protein and beta DNA primers. The results correlated with disease incidence data. Charantia and balsmina RIPs also exhibited antifungal activity against Alternaria alternata and Myrothecium roridum. Inhibition of fungal growth by balsmin RIP @0.250 mg/ml on both fungi varied from 60.09% and 55.10% respectively, where as with charantia RIP 78.8% and 56.2% inhibition respectively was observed. Charantia RIP at 0.500 mg/ml inhibited the mycelial growth to 87.41% and 75.39% respectively. The spore germination inhibition studies revealed an EC50 value of 0.2 mg/ml for both the RIPs. Catalase, peroxidase, total sugars, reducing sugars, proteins, proline and total antioxidant activity increased in RIPs treated plants, highest increase was recorded in plants treated with charantia @0.500 mg/ml, thus depicting the role of RIPs in systemic acquired resistance (SAR). Therefore, the study depicts the antiviral and antifungal activity of RIPs purified from Momordica charantia and Momordica balsmina along with their role in SAR.ennullThesis