Betulinic acid confers antiviral resistance to turnip mosaic virus
through boosting the phytosulfokine signaling in plant
Plant virus disease is one of the most threatening diseases in
agricultural production, and the availability of effective drugs against
viral diseases remains limited. Here, we discovered that betulinic acid
(BA), a pentacyclic triterpenoid derived from natural plants, exhibits
stable resistance to turnip mosaic virus (TuMV) in Nicotiana
benthamiana. Through transcriptomic analysis and RT-qPCR assay, we have
demonstrated that BA treatment specifically induces the expression of
phytosulfokine 3 (PSK3), a plant pentapeptide hormone that fulfills a
wide range of functions, while TuMV infection suppresses its expression.
Further study showed that NbPSK3 positively regulates TuMV infection.
Disruption of PSK signaling by targeting the membrane-bound PSK
receptors (PSKRs) also promotes viral infection. Furthermore, exogenous
PSK treatment could significantly enhance the resistance of N.
benthamiana to TuMV compared with the dPSK or control treatments, and
the silencing receptor NbPSKR1 abolishes the ability of PSK to
inhibit TuMV infection. Meanwhile, BA inhibition of TuMV infection is
dependent on PSK-PSKR signaling pathway. Overall, these results not only
highlight the potential of BA as a promising and environmentally
friendly agent for preventing plant viral diseases but also emphasize
the importance of the PSK signaling pathway in enhancing TuMV resistance
for crop improvement.