Abstract:

Virus-induced gene silencing（VIGS）system is a very useful tool for evaluating gene function and molecular mechanism. Many factors，such as vector，viral proliferation and systemic movement throughout the plant，affect the efficiency of VIGS. In order to improve the VIGS silence efficiency in eggplant（Solanum melongena L.），three parameters（environment temperature，seedling age and gene fragment size）were optimized. The results showed that the silencing efficiency was higher in temperature controlled greenhouse[（25 ± 3）℃，daytime and（20 ± 2）℃，night]than in room temperature greenhouse. After inoculation of the cotyledons of eggplant，the plants had obvious silence symptom，but there was no obvious silence effect when the six-week-old true leaves were inoculated. The silence frequencies of the gene fragments 597 bp，442 bp and 205 bp were 56.67%，62.5% and 68.75% respectively，indicating that about 200 bp might be the most suitable fragment size for VIGS. Then，the function of SmIAA19 from eggplant IAA family genes was evaluated using this VIGS system. The SmIAA19 silence plants presented obvious phenotypic symptoms after inoculation for 4 weeks. The transcript levels of SmIAA19 and auxin content in the SmIAA19 silenced plants were significantly reduced compared to the control. It showed that SmIAA19 was an auxin metabolic related gene in eggplant，and TRV-VIGS system was a reliable method for the function identification of eggplant gene.

Key words: eggplant, Tobacco rattle virus（TRV）, virus-induced gene silencing（VIGS）, SmIAA19