Fig 1.
The roles of plant hormones in virus infections.
The plant hormones shown in ovals generally have positive (red arrows) or negative (blue blocked lines) effects on different viruses in terms of replication, accumulation, symptom development, virus movement, host resistance, and the relationship between virus and insect vectors. For details, see text. ABA, abscisic acid; BaMV, bamboo mosaic virus; BCTV, beet curly top virus; BR, brassinosteroid; CaMV, cauliflower mosaic virus; ChiVMV, Chilli veinal mottle virus; CK, cytokinin; CMV, cucumber mosaic virus; ET, ethylene; GA, gibberellic acid; JA, jasmonic acid; ORMV, oilseed rape mosaic virus; RBSDV, rice black streaked dwarf virus; RDV, rice dwarf virus; RRSV, rice ragged stunt virus; RSV, rice stripe virus; SA, salicylic acid; TBSV, tomato bushy stunt virus; TCV, turnip crinkle virus; TMV, tobacco mosaic virus; TNV, tobacco necrosis virus; ToMV, tomato mosaic virus; TuMV, turnip mosaic virus; TVCV, turnip vein clearing virus; TYLCV, tomato yellow leaf curl virus; WClMV, white clover mosaic virus.
Fig 2.
Plant hormone–virus interactions.
Different virus proteins and host factors interact and lead to positive (arrows) or negative (blocked lines) effects on plant hormone biosynthesis or signaling pathways. The roles of SA, JA, and ET in plant defense responses have been intensively studied. Auxin and GAs are mainly related to the host phenotype after virus infection. CKs and BRs are involved in plant–virus interactions. Different plant hormones display synergetic or antagonistic crosstalk during plant–virus interactions, and microRNAs are used by viruses to target plant hormone pathways. For details, see text. ABA, abscisic acid; AMV, alfalfa mosaic virus; BIN2, BRASSINOSTEROID-INSENSITIVE 2; BR, brassinosteroid; CaMV, cauliflower mosaic virus; CK, cytokinin; ET, ethylene; GA, gibberellic acid; GID2, GIBBERELLIN-INSENSITIVE DWARF2; JA, jasmonic acid; PVY, potato virus Y; RBSDV, rice black streaked dwarf virus; RDV, rice dwarf virus; RRSV, rice ragged stunt virus; RSV, rice stripe virus; SA, salicylic acid; SAMS1, S-adenosyl-l-methionine synthase 1; TMV, tobacco mosaic virus; TuMV, turnip mosaic virus.
Fig 3.
The role of JA and auxin in plant–virus interactions.
(A) The role of JA in plant–virus interactions. Geminivirus C2 binds to CSN5 and affects the activity of SCFs, thus suppressing the JA response to viral infection [28]; RRSV and SRBSDV infection induces miR319, which reduces the function of TCP21 and consequently suppressing JA-mediated defense to facilitate virus infection and symptom development [31]; The RSV CP increases the JA level, resulting in the degradation of JAZ proteins and the release of JAMYB. JAMYB binds to and activates the AGO18 promoter, enhancing host antiviral defense by sequestering miR168 and miR528 and releasing AGO1 and ROS [27]. RSV infection also inhibits the BR signaling pathway and increases the accumulation of OsGSK2, which interacts with and phosphorylates OsMYC2 for degradation and therefore reduces JA-mediated RSV resistance [108]. (B) The role of auxin in plant–virus interactions. The TMV 126 kDa protein interacts with IAA26 and disrupts its localization, thus regulating auxin response during disease development [78]; The RDV P2 protein disrupts auxin signaling by interacting with OsIAA10, thus causing infected plants to display typical viral symptoms [14]; RSV P2 and RBSDV SP8 target OsARF17 and disrupt its dimerization and DNA binding activity, thus manipulating auxin signaling to facilitate infection [83]. AGO18, ARGONAUTE 18; BR, brassinosteroid; JA, jasmonic acid; JAMYB, JA-induced MYB; JAZ, JA ZIM domain; RBSDV, rice black streaked dwarf virus; RDV, rice dwarf virus; ROS, reactive oxygen species; RRSV, rice ragged stunt virus; RSV, rice stripe virus; SCF, Skp–Cullin–F-box; SRBSDV, southern rice black-streaked dwarf virus; TCP, TEOSINTE BRANCHED/CYCLOIDEA/PCF; TIRI, transport inhibitor response protein 1; TMV, tobacco mosaic virus.
Table 1.
Summary of marker genes and quantitive methods of phytohormones in plant–virus interactions.