Therapeutic Delivery of Nanoscale Sulfur to Suppress Disease in Tomatoes: In Vitro Imaging and Orthogonal Mechanistic Investigation

Nanoscale sulfur can be a multifunctional agricultural
amendment
to enhance crop nutrition and suppress disease. Pristine (nS) and
stearic acid coated (cS) sulfur nanoparticles were added to soil planted
with tomatoes (Solanum lycopersicum) at 200 mg/L
soil and infested with Fusarium oxysporum. Bulk sulfur,
ionic sulfate, and healthy controls were included. Orthogonal end
points were measured in two greenhouse experiments, including agronomic
and photosynthetic parameters, disease severity/suppression, mechanistic
biochemical and molecular end points including the time-dependent
expression of 13 genes related to two S bioassimilation and pathogenesis-response,
and metabolomic profiles. Disease reduced the plant biomass by up
to 87%, but nS and cS amendment significantly reduced disease as determined
by area-under-the-disease-progress curve by 54 and 56%, respectively.
An increase in planta S accumulation was evident,
with size-specific translocation ratios suggesting different uptake
mechanisms. In vivo two-photon microscopy and time-dependent gene
expression revealed a nanoscale-specific elemental S bioassimilation
pathway within the plant that is separate from traditional sulfate
accumulation. These findings correlate well with time-dependent metabolomic
profiling, which exhibited increased disease resistance and plant
immunity related metabolites only with nanoscale treatment. The linked
gene expression and metabolomics data demonstrate a time-sensitive
physiological window where nanoscale stimulation of plant immunity
will be effective. These findings provide mechanistic understandings
of nonmetal nanomaterial-based suppression of plant disease and significantly
advance sustainable nanoenabled agricultural strategies to increase
food production.