Tomato trichomes, with unicellular and multicellular types, function as mechanical and chemical barrier against pests. Knock-down and over-expressed lines of SlARF4 were obtained to study the function in trichome formation in tomato. SlARF4-up-regulated plants exhibited increased density of type I, V and VI trichomes, whereas down-regulation of SIARF4 decreased density of type I, V and VI trichomes, indicating SlARF4 positively regulated the formation of unicellular and multicellular trichomes in tomato. Over-expression of SlARF4 increase the excretion of α-terpinene, β-phellandrene, γ-elemene, β-caryophyllene and α-humulene, and confers tolerance to spider mites. Down-regulation of SlARF4 decreased the terpenoid excretion and cause susceptibility to spider mites. Knock-down of SlTHM1 gene increase the density of type I and VI trichomes of leaves, indicating SlTHM1 negatively regulates the multicellular trichome formation. SlTHM1 knock-down plants exhibited increased the terpenoid excretion and tolerance to spider mites. SlARF4 targets the AuxRE motif of SlTHM1 genes and inhibits its expression. Knock-down of SlMYB52 gene increase the density of type V trichomes, which demostartes SlMYB52 negatively regulates the unicellular trichome formation. SlARF4 targets the TGA motif of SlMYB52 gene and inhibits its expression. Moreover, SlTHM1 and SlMYB52 target the promoter of SlCycB2 gene and increase its expression. Taken together, our results prove the SlARF4-SlTHM1/SlMYB52-SlCycB2 cascade in transcriptional regulation of the formation of unicellular and multicellular trichomes in tomato. Our results also provide a novel strategy for insect resistance in plants.
Take Away Notes:
• This presentation provides molecular mechanism about the formation of unicellular and multicellular trichomes.
• SlARF4-SlTHM1/SlMYB52-SlCycB2 cascade plays important role in transcriptional regulation of the formation of unicellular and multicellular trichomes in tomato.
• This presentation provides a new strategy for insect tolerance in plants.