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Table 1 Host factors involved in the antiviral defence against geminiviruses

From: Plant responses to geminivirus infection: guardians of the plant immunity

Host Host factor Function Viral factor Geminivirus Precise role in defence response References
Host defence responses
A. thaliana SnRK1 It is a global regulator of energy metabolism during growth and stress conditions Rep TGMV SnRK1 phosphorylates Ser 97 of Rep protein and interferes replication and infection [98]
TrAP CaLCuV SnRK1 phosphorylates AL2 at ser 109 that delays infection process [33]
N. benthamiana PsbP It is a core protein of oxygen-evolving complex that stabilizes Photosystem II βC1 ToLCNDV/RaLCB PsbP binds to the viral genome and reduces virus replication [191]
N. benthamiana ATG8 It is involved in autophagy, mediates protein degradation βC1 CLCuMuV/CLCuMuB ATG8 binds to βC1 and degrades via autophagy thus causes reduction in viral titre [84]
S. lycopersicum ATG8h It is an autophagy factor, mediates protein degradation Rep TLCYnV C1 gets exported to the cytoplasm by ATG8h and degraded which restricts viral infection [66]
N. tabacum RFP1 It is an E3 ligase that mediates protein ubiquitination βC1 TYLCCNV/TYLCCNB RFP1 interaction with βC1 leads to βC1 degradation thus reduces viral infection [65]
S. lycopersicum UBA1 A ubiquitin-activating enzyme, catalyses the first step in 26S proteasomal degradation pathway TrAP TYLCSV Silencing of UBA1 increases viral infection. TrAP protein interacts with UBA1, thus inhibit its defensive activity [71]
A. thaliana EML1 A histone reader protein, represses active transcription by binding on H3K36 modification Viral minichromosome CaLCuV EML1 binds to viral minichromosome and blocks transcription, therefore attenuates infection [39]
S. lycopersicum RPT4a A subunit of 26S proteasome, aid in unfolding target proteins Intergenic region ToLCNDV RPT4a binds to the viral intergenic region and blocks transcription [40]
V. mungo MAPK1 A protein kinase involved in SA mediated defence Not known MYMIV It mediates defence by inducing SA responsive genes [101]
Triticum monococcum GRAB A Geminivirus Rep A-Binding protein. It may have role in plant development RepA WDV GRAB1 and GRAB2 bind to C-terminus of RepA and inhibit replication [193]
N. benthamiana NbSUMO1 A component of SUMOylation system βC1 SyYVCV/
SyYVCB
It promotes ubiquitin mediated degradation of βC1 protein [77]
Host Host factor Function Viral factor Geminivirus Remarks References
Geminivirus adaptations to host defence
N. benthamiana HDA6 It interacts with MET1 and maintains chromatin silencing Pre-coat protein TYLCV Pre-coat protein interfere with MET1 interaction to HDA6 and inhibit TGS [38]
A. thaliana ADK It converts adenosine to AMP which is essential to maintain the methyl cycle during TGS and aid in the activation of SnRK1 TrAP TGMV, BCTV TrAP inactivates ADK and causes TGS suppression and inactivation of SnRK1 defence pathway [34]
A. thaliana SAHH It catalyses the generation of methyl donor during TGS mediated methylation of viral genome βC1 TYLCCNV/TYLCCNB βC1 inhibits SAHH enzyme and suppress TGS [37]
A. thaliana BAM1 It facilitates cell to cell movement of RNAi signals C4 TYLCV C4 interacts with BAM1 domain and inhibits spread of silencing signals [109]
N. benthamiana MKK2
MPK4
Regulates defence responses by via phytohormones, ROS and defence-related gene expression during biotic stress βC1 TYLCCNV/TYLCCNB βC1 inhibits the kinase activity of both MKK2 and MPK4 and increases host susceptibility [90]
A. thaliana SnRK1 It is a global regulator of energy metabolism during growth and stress conditions TrAP TGMV, CaLCuV TrAP inactivates SnRK1 and leads to enhanced susceptibility [97]
BCTV [98]
A. thaliana NIKs It undergoes reversible phosphorylation within its activation loop domain to carry out the defensive function NSP CaLCuV NSP inhibits autophosphorylation of NIK and thus breaks suppression of NIK mediated global protein synthesis [88]
A. thaliana CSN5 It regulates SCF complex activity during ubiquitination TrAP TYLCV, TYLCSV TrAP interacts with CSN5 and impairs SCF complex function thereby inhibits jasmonic acid signalling and enhanced infection [72]
N. benthamiana NbSUMO1 A component of SUMOylation system βC1 SyYVCV/SyYVCB It stabilises the βC1 protein [77]