Characterization of Sirnas Derived from Two Species of Cassava-Infecting Geminiviruses in Nicotiana Benthamiana

Abstract

The infection dynamics of cassava mosaic geminiviruses was determined in Nicotiana benthamiana. Following inoculation, symptoms were observed at 5 and 10 dpi for African cassava mosaic virus (ACMV-CM) and the Kenyan strain K201 of East African cassava mosaic virus (EACMV KE2 [K201]). Northern and Southern blots indicated higher accumulation of ACMV-CM at 10 dpi compared with EACMV KE2 (K201) correlating with more severe symptoms at this time point. However, unlike for EACMV KE2 (K201), symptom remission characterized by appearance of non-asymptomatic leaves was observed after 20 dpi in plants infected with ACMV-CM. Deep sequencing identified between 969,015 and 1,307,689 total reads of which >80% mapped to the host genome. For both virus species, 22 nt virus derived sRNAs (vsRNAs) reads were the most abundant (34% - 53%) followed by 21 nt (27% - 27%) and 24 nt (9 – 23%) vsRNA reads. EACMV KE2 (K201) vsRNAs were proportionally higher (12.31% and 4.51%) than those derived from ACMV-CM (5.70% and 0.45%) for DNA A and DNA B respectively. vsRNAs were covered the entire virus genome with dense accumulation at regions where the viral ORFs overlapped.

Key words; RNA interference, Cassava mosaic disease, Geminiviruses

DOI: 10.7176/JNSR/10-8-06

Publication date: April 30^th 2020