Gene Expression And Their Functions Of Heat Shock Proteins In Invasion Whitefies

Bemisia tabaci (Gennadius), called a"superbug", has been reported to distribute over 90 countries in the world, the study of invasive mechanism has been aroused widely. Asymmetric mating interactions promote widespread invasion and displacement of indigenous B. tabaci population by the invasive biotype B. Mutualism between B. tabaci biotype B and begomoviruses via its host plants speed up widespread invasion. B. tabaci biotype B has a wide range of host plants make its invasion into new environmental location successful. Bemisia tabaci was found in China in 1949 and was not considered an important pest until the recent invasion of B. tabaci biotype B and biotype Q, which has been found in most provinces of China and become a severe pest of numerous field and ornamental crops. Why the indigenous B. tabaci biotype ZHJ1 and ZHJ2 were not widespread in China? What different between the invasive biotype and indigenous biotype?Temperature is an important factor that determines the distribution and expansion of a species. Our work to study the relation between hsp espression level and differential thermotolerent abilities in invasive biotype (biotype B and biotype Q) and indigenous biotype (biotype ZHJ1 and biotype ZHJ2), RNAi study proved that hsp play key roles for thermotolerence in whiteflies.The hsp expression profile results showed that temperatures for onset (Ton) or maximal (Tmax) induction of hsp expression in T. vaporariorum were generally 2~6℃lower than those in B. tabaci biotype B. These results suggest that the Ton (or Tmax) of hsps can represent the differences in temperature tolerance of these two whitefly species, and may be used to determine their natural geographical distribution and natural population seasonal dynamics. Our work found that B. tabaci biotype B and biotype Q were more heat and cold resistant than biotype ZHJ1, the hsp expression inductively Ton or Tmax in B. tabaci invasive biotype (biotype B and biotype Q) were generally 2~4℃higher than those in indigenous biotype ZHJ1. Another indigenous B. tabaci biotype ZHJ2, Its thermotolerent abilities has not different with biotype ZHJ1, the hsp expression inductively Ton or Tmax in indigenous biotype ZHJ2 were generally 2℃lower than those in B. tabaci invasive biotype (biotype B and biotype Q). hsp23, hsp70 and hsp90 mRNA levels were significantly decreased in both T. vaporariorum and B. tabaci biotype B after injection of dsRNA for 24h.RNAi study proved that hsp23 and hsp70 play key roles for thermotolerence in T. vaporariorum but not in B. tabaci biotype B cold tolerence, and hsp90 showed no significant roles for thermotolerence in both whiteflies species.Our work try to establish a theory of invasive mechanism in B. tabaci, the higher hsp expression Ton or Tmax promote the invasive biotype thermotolerence, conduces to B. tabaci biotype B and biotype Q have a strong ability to stress environment, accelerated the population broadly distributed and amount increased.