Abstract

Characterizing anti-virus genes in sweetpotato is a vital step in mitigating yield loss due to virus infections. This work lays an insight into the structure and expression of key anti-virus genes. Related plant-based anti-virus genes were used as reference to mine key sweetpotato genes from various databases. BLASTN and BLASTP for transcripts was done for evaluation of phylogenetic relationship. Eight genes were identified: RNA dependent RNA polymerases (RDR) 1, 2, 5 and 6; Argonaute 1; and Dicer-like 1, 2 and 4, with more variants for RDR1 transcripts. Phylogenetically, RDR defense genes evolved more recently than other genes. Given the big number of variants and recent evolution of RDRs, further analysis for DLDGD or DFDGD catalytic domains, organization of coding sequences and gene expression were done on RDRs. DLDGD or DFDGD were observed in RDRs with the exception of IbRDR1c_Ch1_1623 and RDR2_Chr2_1059. RDR1 variants revealed varying exon-intron organization, and the IbRDR1c_Ch1_1623 transcript had no introns. High titres for IbRDR1a_Chr8_3068, IbRDR1b_Chr8_3014 and IbRDR1d_Chr8_1149 were observed in SPVC-infected plants suggesting these RDRI variants are involved in resistance against virus infection. The titre of IbRDR1c_Chr1_1623 was not affected. This study offers an opportunity for molecular breeding and selection of cultivars for distribution to farmers.

Key words: Virus defense genes, gene silencing, RNA dependent RNA polymerases (RDR), catalytic domain, titre.