Table 2.

Summary of putative effectors in virus-vector interactions, cellular targets,and ecological consequences

Effector	Virus or Vector Origin	Plant Targets and Mechanism	Plant Species	Subcellular Location	Impact on Virus/Vector	References
Target 1: Transcription factors
Viral effectors
βC1	Betasatellite of TYLCCNV	Disrupts MYC2 dimerization and glucosinolate defenses downstream of JA	N. tabacum	Nucleus	Increases B. tabaci performance	Li et al. (2014a)
βC1	Betasatellite of TYLCCNV	Interacts with and enhances repressive activity of AS1 attenuating PDF1.2 and PR4 expression	A. thaliana	Nucleus	Increases B. tabaci performance	Yang et al. (2008)
βC1	Betasatellite of TYLCCNV	Disrupts PIF and MYC2 dimerization and reduces terpene synthase and volatile production	A. thaliana	Nucleus	Increases B. tabaci attraction	(Zhao et al., 2021)
βC1	Betasatellite of CLCuMuV and betasatellite of TYLCCNV	Disrupts homeo-dimerization of WRKY20 and WRKY20-ORA59 dimerization to alter glucosinolate profiles in vascular tissue and leaves	N. benthamiana, A. thaliana, Gossypium barbadense	Nucleus	Increases B. tabaci performance, decreases performance of M. persicae and H. armigera	Zhao et al. (2019)
Vector effectors
Bsp9	B. tabaci	Suppresses DAMP-triggered immunity induced by Pep1; Interacts with WRKY33, and MPK6	A. thaliana, N. benthamiana, S. lycopersicum	Cytoplasm	Increased B. tabaci and TYLCV performance	Wang et.al. (2019)
Bt56	B. tabaci	Interacts with KNOX transcription factor and increases SA and SA-related transcripts	N. tabacum, N. benthamiana	Nucleus	Increased B. tabaci performance	Li et al. (2014a)
Target 2: Protein degradation pathways
Virus effectors
C2	TYLCV	Interacts with the ubiquitin precursor, RPS27A, to prevent JAZ1 degradation and MYC2 and terpene synthase induction	N. tabacum	Nucleus	Increases B. tabaci performance	Li et al. (2019)
2b, 2a, 1a	CMV	2b interacts with JAZ proteins to prevent degradation and induction of downstream signaling and volatiles, 2b also suppresses AGO1, which is stabilized by 1a. 2a increases CYP81F2 expression and the production of glucosinolates	A. thaliana	Nucleus, cytoplasm, processing bodies	Increases M. persicae attraction before contact and increases dispersal after contact	Westwood et al. (2013) ; Wu et al. (2017)
Vector effectors
Mp1	M. persicae	Interacts with and reduces protein levels of the plant trafficking pathway protein VPS52	N. benthamiana, A. thaliana	Prevacuolar compartments	Increases M. persicae performance	Pitino and Hogenhout (2012); Rodriguez et al. (2017)
Target 3: Re-localization of proteins
Virus effectors
NIa-Pro	TuMV, PVY	Localizes outside of nucleus to inhibit plant defenses, increases ethylene production and inhibts callose accumulation	A. thaliana,   N. benthamiana	Nucleus, vacuole	Increases fecundity of M. persicae	Casteel et al. (2014); Bak et al. (2017)
Target 4: Signal transduction
Vector effectors
Me10	M. eurphorbiae,   A. gossypii	Interacts withTFT7 protein, mechanisms unknown	S. lycopersicum,   N. benthamiana	Cytoplasm, nucleus	Increased M. eurphorbiae fecundity	Atamian et al. (2013); Chaudhary et al. (2014)
ApHRCs	A. pisum	Serratia symbiotica induction of ApHRC possibly suppresses Ca2+, ROS, and JA/SA- related transcript induction	M. truncatula	Unknown	Increased A. pisum feeding duration	Wang et al. (2020)
BtFer1	B. tabaci	BtFer1 exhibits Fe2+ binding ability and ferroxidase activity, suppresses H2O2 and, callose production, proteinase inhibitor activation, and JA signaling	S. lycopersicum	Phloem	Increased performance of B. tabaci	Su et al. (2019)
Target 5: Detoxification of secondary metabolites
Vector effectors
Me47	M. eurphorbiae	Me47 encodes a glutathione S-transferase (GST), that was shown based on enzymatic activity to detoxify isothiocyanates	N. benthamiana, S. lycopersicum	Unknown	Increases M. euphorbiae fecundity on tomato, inhibits M. persicae performance on N. benthamiana	Atamian et al. (2013); Chaudhary et al. (2014)
AcDXR	A. craccivora	AcDXR is a diacetyl/L-xylulose reductase that detoxifies the plant secondary metabolite methylglyoxal	V. radiata,   P. sativum	Phloem	Increases A. craccivora fecundity	MacWilliams et al. (2020)
Laccase1	B. tabaci	Laccase 1 is a polyphenol oxidase that might help whiteflies overcome chemical defenses	S. lycopersicum	Unknown	Increased performance of B. tabaci	Yang et al. (2017)
Target 6: The unknowns
Virus effectors
P0, P1, P7	PLRV	Unknown	S. tuberosum	Cytoplasm (P1), nucleus (P0)	Increases performance and preference of M. persicae	Prüfer et al. (1999); Patton et al. (2020)
HC-Pro	TuMV	Unknown	N. benthamiana	Cytoplasm	Decreases M. persicae performance	Maia et al. (1996); Casteel et al. (2014)
NIa-Pro	TuMV	Increases free amino acid levels in plants	A. thaliana, N. benthamiana	Nucleus, vacuole	Unknown	Casteel et al. (2014)
6K1	TuMV	Unknown	N. benthamiana	Chloroplast	Decreases M. persicae performance	Casteel et al. (2014); Hongguang et al. (2021)
VPg	TuMV	Unknown	N. benthamiana	Cytoplasm and nucleus	Decreases M. persicae performance	Schaad et al. (1996); Casteel et al. (2014)
Vector effectors
Mp10	M. persicae	Induces the hypersensitive response in an SGT1-dependent manner and suppresses flg2- induced PTI	N. benthamiana	Mesophyll cells next to feeding tracks	Over-expression in plants reduces M. persicae fecundity	Bos et al. (2010)
Mp56, Mp57, Mp58	M. persicae	Unknown	A.thaliana,   N. benthamiana	Unknown	Over-expression in plants reduces M. persicae fecundity	Elzinga et al. (2014)
Mp2	M. persicae	Unknown	A. thaliana,   N. benthamiana	Unknown	Over-expression in plants reduces M. persicae fecundity	Pitino and Hogenhout (2012)
Mp42	M. persicae	Unknown	N. benthamiana	Unknown	Over-expression in plants reduces M. persicae fecundity	Bos et al. (2010)
MpC002, ApC002	M. persicae,   A. pisum	Unknown	Vicia faba,   A. thaliana,   N. benthamiana	Sieve elements	Over-expression in plants increases aphid performance/fecundity	Mutti et al. (2008); Bos et al. (2010)
Armet	A. pisum	Transient expression induces SA accumulation in plants	N. benthamiana	Probably in sieve elements	Knockdown in A. pisum shortens their lifespan	Wang et al. (2015a)
MIF1	A. pisum	Suppresses callose formation, the hypersensitive response, and defense-related transcript induction	N. benthamiana	Unknown	Over-expression in plants increased A. pisum fecundity	Naessens et al. (2015)
Ap25	A. pisum	Unknown	P. sativum	Unknown	Over-expression increases A. pisum fecundity	Guy et al. (2016)
S2G4, 6A10, 2G5	B. tabaci	The three effectors induced SA-responsive genes PR1a, PR2	N. benthamiana	Unknown	Unknown on aphids, but suppresses pathogens X. axonopodis pv. vesicatoria and R. solanacearum	Lee et al. (2018)
ACEs	A. pisum	Unknown	V. faba	Unknown	Knockdown of ACE1 and ACE2 decreases A. pisum fecundity	Wang et al. (2015b)
Me23	M. eurphorbiae	Unknown	N. benthamiana	Unknown	Over-expression in plants increases M. eurphorbiae fecundity	Atamian et al. (2013)