RT Journal Article
SR Electronic
T1 Characterization by Next Generation Sequencing Reveals the Molecular Mechanisms Driving the Faster Evolutionary rate of <em>Cassava brown streak virus</em> Compared with <em>Ugandan cassava brown streak virus</em>
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 053546
DO 10.1101/053546
A1 Titus Alicai
A1 Joseph Ndunguru
A1 Peter Sseruwagi
A1 Fred Tairo
A1 Geoffrey Okao-Okuja
A1 Resty Nanvubya
A1 Lilliane Kiiza
A1 Laura Kubatko
A1 Monica A Kehoe
A1 Laura M Boykin
YR 2016
UL http://biorxiv.org/content/early/2016/05/16/053546.abstract
AB Cassava is a major staple food for 800 million people. Cassava brown streak disease (CBSD), is caused by Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV) is suppressing cassava yields in East Africa at an alarming rate. Previous studies have documented CBSV is more devastating than UCBSV. This is because CBSV is harder to breed resistance for, causes more infections and yield losses in cassava, and its species delimitation is more challenging. We set out to characterize the CBSV and UCBSV whole genomes from the 26 previously published genomes and three new from Uganda, using NGS data with the goal of uncovering genetic patterns that explain the observed biological differences. In this paper, we report phylogenetic relationships, rates of synonymous and non-synonymous substitutions, and whole genome-based evolutionary rates for CBSV and UCBSV. Using the whole genome sequences we produced the first coalescent based species tree estimation for CBSV and UCBSV which supports previously published studies pointing to multiple species of both CBSV and UCBSV. This new species framework led to the finding that CBSV has a faster rate of evolution when compared with UCBSV. The genes responsible for CBSV’s rapid rate of evolution are NIa, 6K2, NIb and P1. Furthermore, we have discovered that for CBSV, rates of nonsynonomous substitutions are more predominant than synonymous substitution and occur across the entire genome. All comparative analyses between CBSV and UCBSV presented suggests CBSV is outsmarting the cassava immune system, thus is more devastating and harder to control.