Cassava brown streak disease (CBSD) is a severe virus disease of cassava and prevalent in the eastern regions of Africa. The disease is characterized by distinct vein chlorosis and streak symptoms on leaves and stems and necrosis of storage roots. This necrosis can encompass large areas of the root, rendering it inedible so that the entire cassava harvest can be lost. African cassava varieties are susceptible to either of the two viruses causing the disease, cassava brown streak virus (CBSV) and Uganda cassava brown streak virus, and while there are less sensitive varieties, all cassava eventually succumb to the disease. The lack of CBSD resistance in African cassava varieties prompted this search for new sources of virus resistance in the diversity of South American cassava germplasm held in the collection at International Center for Tropical Agriculture, Columbia. Our search for CBSD resistance in South American cassava germplasm accessions revealed that most of the 238 South American cassava lines infected with CBSV established systemic virus infections with moderate to severe disease symptoms on leaves and stems. Fifteen cassava accessions did not become virus infected, remained free of symptoms, and CBSV was undetected by qRT-PCR. When tuberous roots of those lines were examined, necrotic tissue was found in eight lines and CBSV was detected. The remaining seven cassava accessions remained clear of symptoms on all tissues and organs and were virus free. A broad spectrum of virus resistance also including other virus isolates was confirmed for the breeding lines DSC167 and DSC118. While detailed infection experiments with other cassava lines selected for resistance are still ongoing, this indicates that the resistance identified may also hold against a broader diversity of CBSVs. Taken together, we present the results of a comprehensive study on CBSV resistance and susceptibility in cassava germplasm accessions from South America. The virus resistance in cassava germplasm identified provides compelling evidence for the invaluable contribution of germplasm collections to supply the genetic resources for the improvement of our crops.

High confidence definition of protein interactions is an important objective toward the understanding of biological systems. Isotope labeling in combination with affinitybased isolation of protein complexes has increased in accuracy and reproducibility, yet, larger organisms-including humans-are hardly accessible to metabolic labeling and thus, a major limitation has been its restriction to small animals, cell lines, and yeast.As composition as well as the stoichiometry of protein complexes can significantly differ in primary tissues, there is a great demand for methods capable to combine the selectivity of affinity-based isolation as well as the accuracy and reproducibility of isotope-based labeling with its application toward analysis of protein interactions from intact tissue.Toward this goal, we combined isotope coded protein labeling ( Classical antibody-based strategies to determine protein interactions have long been hampered by the fact that most binders exhibit unspecific binding. Immunoprecipitationsthe most widely used method-not only suffer from nonspecific binding because of compromised selectivity and specificity of the immunoglobulin, but also from nonspecific binding to the carrier beads. Because of this lack of specificity, a large proportion of reported protein interactions in the literature as well as in databases that gather interaction data are likely to be compromised by false positives. Furthermore, despite great advancements in sensitivity and accuracy of mass spectrometers and peptide separation techniques, mass spectrometry-based identifications usually fail to detect lowabundance members of protein complexes, medium affinity or transient binders. Several methods have tackled these problems. Tandem affinity purification (TAP) has resulted in an unprecedented specificity, concerning protein interaction data (1, 2). Yet this method is limited by the fact that recombinant expression of a TAP-fusion protein is required and additionally hampered by the risk that exogenous expression of the bait protein of interest may result in an artificial change of stoichiometries.To circumvent these drawbacks, Selbach and Mann developed a quantitative immunoprecipitation, combined with RNAi (QUICK), using stable isotope labeling with amino acids in cell culture (SILAC) to gain improved selectivity (3-5). The main advantage of QUICK is that endogenous protein stoichiometries are the basis for immunoprecipitation, for the first time allowing one to accurately monitor protein interactions at endogenous protein concentrations from living cells and discriminate true positive from false positive interactions. Yet this method requires metabolic isotope labeling of whole organisms or reference cells, as described for SuperSILAC, to allow comparative analysis of two protein sets (6). Metabolic labeling, especially when applied to living organisms, requires feeding them with isotopic food (7-9). The procedure of la- 1 The abbreviations used are: SILAC, stable isotopic labeling with amino acids in cell culture; ICP...

Vaccines are central to controlling the coronavirus disease 2019 (COVID-19) pandemic but the durability of protection is limited for currently approved COVID-19 vaccines. Further, the emergence of variants of concern (VoCs) that evade immune recognition has reduced vaccine effectiveness, compounding the problem. Here, we show that a single dose of a murine cytomegalovirus (MCMV)-based vaccine, which expresses the spike (S) protein of the virus circulating early in the pandemic (MCMVS), protects highly susceptible K18-hACE2 mice from clinical symptoms and death upon challenge with a lethal dose of D614G SARS-CoV-2. Moreover, MCMVSvaccination controlled two immune-evading VoCs, the Beta (B.1.135) and the Omicron (BA.1) variants in BALB/c mice, and S-specific immunity was maintained for at least 5 months after immunization, where neutralizing titers against all tested VoCs were higher at 5-months than at 1-month post-vaccination. Thus, cytomegalovirus (CMV)-based vector vaccines might allow for long-term protection against COVID-19.