The Effect Of Temperature And Host On The Body Size Of Trichogramma Dendrolim (Matsumura) And Expression Level Of FoxO Gene

Egg parasitoid wasps played an important role in the pest biology control because of the ability of leading death of host eggs. Egg parasitoid wasps always have smaller body size restricted by the restriction of host egg size. Body size is one of the fitness indicators of egg parasitoid wasps, which correlating with the fertility and parasitic ability of wasps. FoxO transcription factor has involved the regulation of organism development progress as the downstream target of insulin signal pathway. The Trichogramma dendrolim (Matsumura) was used to research the regulatory mechanism of different factors to the egg parasitoids body size. T. dendrolim were reared in two kinds of host eggs at five different temperatures (18℃、22 ℃、 26℃、30℃、33℃). The volume of two kinds of host eggs、the hind tibia length and parasitic capacity of T. dendrolim were detected. The cDNA sequence of β-actin gene and FoxO gene were cloned by RT-PCR and Rapid amplication of cDNA ends (RACE) technology. To investigate the relationship between the body size of T.dendrolim and gene expression of FoxO, the relative expression of FoxO gene in two kinds of T.dendrolim at five different temperatures were detected by qRT-PCR technology. Represented by T.dendrolim, combining the biology phenomenon with gene expression study, this research has provided basis for the study of body size of egg parasitoid wasps. The results were as follows:1 There was significant difference between the hind tibia length of two kinds of T.dendrolim reared in different host eggs. The body size of T.dendrolim reared in Antheraea pernyi egg was significicent larger than T.dendrolim reared in Corcyra cephalonica. The volume of the two kinds of host eggs has significant difference. At five different temperatures, T.dendrolim has the shortest hind tibia length at 26℃, and the T.dendrolim at lower temperatures(18℃、 22 ℃) have larger hind tibia than higher temperatures(30℃、33℃). The weight of 300 T.dendrolim individuals reared in two kinds of host eggs at five temperatures has the same regulation with the hind tibia length. The development time of two kinds T.dendrolim was reduced along with higher temperatures. The two kinds of T.dendrolim has the higestest parasitic capacity and offspring numbers at 26℃, and significient decreased in lower and higher temperatures.2 Partical cDNA sequence of β-actin gene and FoxO gene were cloned by RT-PCR technology.593bp cDNA sequence of β-actin gene was cloneded, encoding 196 amino acid residues. Blasted with the β-actin gene of other insects, the sequence identity were over 87%. The p-actin sequence of T.dendrolim has been submitted to GeneBack, the accession number is KX066242. Based on the conserved sequence of FoxO gene, part of the 3’end and 5’end of the FoxO gene were cloned by RACE technology.1026bp cDNA sequence of FoxO gene was cloned from T.dendrolim, encoding 340 amino acid residues. Via sequence alignment on NCBI, the sequence identity of FoxO gene with other insects were over 80%, and could up to 94% with T. pretiosum. There has three conservation DNA binding sites on the FoxO amino acid sequence. The FoxO gene sequence of T.dendrolim has been submitted to GeneBack, the accession number is KX066243. Therefore, all the results indicated that the sequences cloned from T.dendrolim were β-actin gene and FoxO gene respectively.3 The β-actin gene expressions in two kinds of T.dendrolim at five different temperatures were detected by qRT-PCR technology. The result showed that, there was no significant difference between the expressions of P-actin gene at five different temperatures. However, the expression of P-actin gene between T.dendrolim reared in two kinds host eggs has significant difference. So β-actin gene can used as a control gene under the condition of different temperature effection, but can not used in the condition of different host eggs effection.4 With the β-actin gene as control gene, the relative expression of FoxO gene were detected by qRT-PCR tchnology. The results showed that, compared with T.dendrolim at 26℃, the relative expression of FoxO gene at other temperatures were down-regulated, but there was no significant difference between temperatures. The results indicated that FoxO gene has involved in the regulation of body size of T.dendrolim.