Cowpea lipid transfer protein 1 regulates plant defense by inhibiting the cysteine protease of cowpea mosaic virus

Proc Natl Acad Sci U S A. 2024 Aug 27;121(35):e2403424121. doi: 10.1073/pnas.2403424121. Epub 2024 Aug 19.

Abstract

Many virus genomes encode proteases that facilitate infection. The molecular mechanism of plant recognition of viral proteases is largely unexplored. Using the system of Vigna unguiculata and cowpea mosaic virus (CPMV), we identified a cowpea lipid transfer protein (LTP1) which interacts with CPMV-encoded 24KPro, a cysteine protease, but not with the enzymatically inactive mutant 24KPro(C166A). Biochemical assays showed that LTP1 inhibited 24KPro proteolytic cleavage of the coat protein precursor large coat protein-small coat protein. Transient overexpression of LTP1 in cowpea reduced CPMV infection, whereas RNA interference-mediated LTP1 silencing increased CPMV accumulation in cowpea. LTP1 is mainly localized in the apoplast of uninfected plant cells, and after CPMV infection, most of the LTP1 is relocated to intracellular compartments, including chloroplast. Moreover, in stable LTP1-transgenic Nicotiana benthamiana plants, LTP1 repressed soybean mosaic virus (SMV) nuclear inclusion a protease activity, and accumulation of SMV was significantly reduced. We propose that cowpea LTP1 suppresses CPMV and SMV accumulation by directly inhibiting viral cysteine protease activity.

Keywords: Vigna unguiculata; cowpea mosaic virus; lipid transfer protein; protease inhibitor; viral cysteine protease.

MeSH terms

  • Capsid Proteins / genetics
  • Capsid Proteins / metabolism
  • Carrier Proteins* / genetics
  • Carrier Proteins* / metabolism
  • Comovirus* / genetics
  • Comovirus* / metabolism
  • Comovirus* / physiology
  • Cysteine Proteases / genetics
  • Cysteine Proteases / metabolism
  • Endopeptidases
  • Nicotiana* / genetics
  • Nicotiana* / metabolism
  • Nicotiana* / virology
  • Plant Diseases* / virology
  • Plant Proteins* / genetics
  • Plant Proteins* / metabolism
  • Plants, Genetically Modified
  • Potyvirus / metabolism
  • Potyvirus / physiology
  • Vigna* / metabolism
  • Vigna* / virology
  • Viral Proteins / genetics
  • Viral Proteins / metabolism

Substances

  • Carrier Proteins
  • Plant Proteins
  • Cysteine Proteases
  • lipid transfer protein
  • Viral Proteins
  • Capsid Proteins
  • nuclear inclusion protein a, mosaic viruses
  • Endopeptidases

Supplementary concepts

  • Soybean mosaic virus