Effects of Low Concentration Methyl Jasmonate on Initiation and Development of Long-stalk Glandular Trichomes in Tobacco

Methyl jasmonate (MeJA) has a strong induction effect on the initiation of long-stalk glandular trichomes in tobacco, but the development of tobacco seedlings can be inhibited by high concentration MeJA. To study the effects of low concentration MeJA on the development of glandular trichomes and trichome secretions, and to explore the responsive patterns of related genes, Nicotiana tabacum cv. Yunyan 87 seedlings at three-leaf stage were separately sprayed with MeJA at different concentrations. The results showed that the density and glandular head of long-stalk glandular trichomes increased gradually with the increase of MeJA concentrations. Among them, 300 μmol/L MeJA had a significant effect on induction of long-stalk glandular trichomes, and had no effect on leaf development. When treated with high concentration MeJA (600 μmol/L MeJA), the growth and development of leaves were inhibited. Analysis of the chemical components on leaf surface showed that the contents of cembranoids, alkanes and sucrose esters were nearly doubled after sprayed with 300 μmol/L MeJA. qRT-PCR was used to study the gene expression pattern after MeJA treatments. It was found that the key genes related to cembranoid biosynthesis CBTS and CYP71D16, as well as the lipid transporter gene NtLTP1, were activated by MeJA treatments. The expressions of ARF3, GIS, CD2, Wo and CycB2, which may regulate the initiation of glandular trichomes, were responsive to MeJA treatments. Among them, ARF3 and GIS were induced by MeJA, while CD2, Wo and CycB2 were repressed by MeJA. These results indicated that 300 μmol/L MeJA can regulate the expression of genes related to glandular trichome development, and thus safely and effectively promote the initiation and development of long-stalk glandular trichomes and trichome secretion synthesis.