Differential Transmission of Old and New World Begomoviruses by Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) Cryptic Species of Bemisia tabaci

Abstract

Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) are two of the most invasive members of the sweetpotato whitefly, Bemisia tabaci, cryptic species complexes and are efficient vectors of begomoviruses. Bemisia tabaci MEAM1 is the predominant vector of begomoviruses in open-field vegetable crops in the southeastern United States. However, recently B. tabaci MED also has been detected in the landscape outside of greenhouses in Florida and Georgia. This study compared the transmission efficiency of one Old-World (OW) and two New-World (NW) begomoviruses prevalent in the southeastern United States, viz.., tomato yellow leaf curl virus (TYLCV), cucurbit leaf crumple virus (CuLCrV), and sida golden mosaic virus (SiGMV) between B. tabaci MEAM1 and B. tabaci MED. Bemisia tabaci MEAM1 efficiently transmitted TYLCV, CuLCrV, or SiGMV, whereas B. tabaci MED only transmitted TYLCV. Percent acquisition and retention of OW TYLCV following a 72 h acquisition access period was significantly higher for B. tabaci MED than B. tabaci MEAM1. In contrast, B. tabaci MEAM1 acquired and retained significantly more NW bipartite begomoviruses, CuLCrV or SiGMV, than B. tabaci MED. Quantitative analysis (qPCR) of virus DNA in whitefly internal tissues revealed reduced accumulation of CuLCrV or SiGMV in B. tabaci MED than in B. tabaci MEAM1. Fluorescent in situ hybridization (FISH) showed localization of CuLCrV or SiGMV in the midgut of B. tabaci MED and B. tabaci MEAM1. However, localization of CuLCrV or SiGMV was only observed in the primary salivary glands of B. tabaci MEAM1 and not B. tabaci MED. TYLCV localization was observed in all internal tissues of B. tabaci MEAM1 and B. tabaci MED. Overall, results demonstrate that both B. tabaci MEAM1 and B. tabaci MED are efficient vectors of OW TYLCV. However, for the NW begomoviruses, CuLCrV and SiGMV, B. tabaci MEAM1 seems to a better vector.

Differential Transcriptional Responses in Two Old World Bemisia tabaci Cryptic Species Post Acquisition of Old and New World Begomoviruses

“…This study assessed the differences in gene expression in B. tabaci MEAM1 and MED whiteflies in response to the acquisition of Old and New World begomoviruses. Both the Old and New World viruses examined in this study were transmitted by the B. tabaci MEAM1 cryptic species, and only the Old World virus (TYLCV) was transmitted by the B. tabaci MED cryptic species [36]. Gene expression differences were compared between the two cryptic species following the acquisition of TYLCV, SiGMV, or CuLCrV.…”

“…More transcriptional changes were associated with TYLCV acquisition (MEAM1-462 genes and MED-413 genes), followed by SiGMV acquisition (MEAM1-459 genes and MED-165 genes), whereas CuLCrV acquisition (MEAM1-69 genes and MED-44 gene) induced the least number of transcriptional changes. Both TYLCV and SiGMV accumulated at significantly higher levels (copies per ng DNA) in both their host plants and vector's tissues (midgut, hemolymph, and salivary glands), while CuLCrV accumulated at significantly lower amounts in its host plant and vector's tissues [30,36]. Bemisia tabaci MEAM1 transmits SiGMV and CuLCrV, and their circulative tropism in whiteflies could have facilitated binding with different whitefly proteins and putative receptors, leading to increased transcriptional changes [22,72,73].…”

“…The virus isolates used in this study are described extensively in Gautam et al [36]. Briefly, the TYLCV isolate was collected in 2009 from a commercial tomato farm located in Montezuma in Macon County in GA, USA.…”

“…A week post inoculation, all of the leaves were removed. The infection status of plants in insect-free newly-emerged leaves was evaluated at ~3 weeks post inoculation by endpoint PCR using species-specific primers [36,39].…”

“…In these cropping systems, B. tabaci MEAM1 is known to transmit tomato yellow leaf curl virus (TYLCV), sida golden mosaic virus (SiGMV), and cucurbit leaf crumple virus (CuLCrV), which cause diseases [32,33]. In laboratory studies, B. tabaci MED tissues accumulated reduced amounts of the two New World begomoviruses compared to B. tabaci MEAM1 and did not transmit SiGMV and CuLCrV, albeit it was an efficient vector of TYLCV [34][35][36]. Molecular and cellular factors underlying the differential transmission of these and several other begomoviruses by the B. tabaci MEAM1 and MED have not been elucidated, and studies identifying their primary transmission determinants are critical.…”