The Transcriptomes And Cuticular Protein Gene Expression Of The Reproductives In Reticulitermes Labralis

Caste differentiation in termites is one of the most conspicuous examples of facultative polyphenism in animals. The reproductive caste of many termite species, especies Reticulitermes, exhibits remarkable plasticity. In R.labralis (Hisa), the last instar nymphs can develop in three manners:(i) via a single moult into adultoid reproductives (AN), and (ii) via a single moult into brachypterous neotenics (BN), and (iii) via a single moult into alate reproductives (AR). Little is known about the functional genes and mechanism of reproductive division that underlies caste differentiation. In the present study, we sequenced and compared the transcriptome profiles of the three different reproductive castes, that is, AN, BN and AR, from the last instar nymphs of R.labralis and subsequently quantified the differential expressions of cuticular protein gene. The results were showed as following:1. The genes expression level of cuticular sclerotization and pigment deposition in AR was higher than that of AN and BN. There was no significant difference in the length of bodies in AN, BN and AR, but the length of wings in AR was higher than that of AN and BN.2. During the moulting and differentiation process from last instar nymphs to AN, BN and AR, the development of oocytes was in growth stage. Before the swarming, the oocytes in AR had matured in order to reduce work load and improve the survival rate.3. We constructed RNA-seq libraries using mRNA isolated from three reproductive castes. A total of 404,152,188 clean sequencing of reads were abtained by Hi-SeqTM 2000 (Illrnina) paired-end sequencing of the R.labralis. Based on the clean reads, a total of 61,953 unigenes, ranging from 201 bp to 17,328 bp were assembled by the Trinity program, with a mean length of 905 bp.17,444 unigenes had significant matches in the Nr database,13,178 unigenes had significant matches in the Swiss-prot database,5,901 unigenes had significant matches in the COG database,6,784 unigenes had significant matches in the KEGG database. Compared the different expression genes of AN and BN,38 unigenes have changed included 26 up-regulated unigenes and 12 down-regulated unigenes; For AN and AR,4613 unigenes have changed included 3358 up-regulated unigenes and 1255 down-regulated unigenes; For BN and AR,3933 unigenes have changed included 2269 up-regulated unigenes and 1664 down-regulated unigenes. It was the first time to complish the RNA sequencing of R. labralis. Beacuse of the relatively short length of distinct gene sequences and lacking genome information in R.labralis, most of the 61,953 assembled sequences could not be matched to known genes (71.54%). These unigenes could also be R.labralis specific genes.4. We performed qRT-PCR analysis of the 7 cuticular protein genes in the AR, AN and BN. We demonstrated that two RR-2 genes were expressed in higher levels in primary reproductives than in secondary reproductives. The transcription level of RR-2 motif 67 of AR was 166-fold and 2064-fold higher than that of AN and BN, respectively; the transcription level of RR-2 number 15 of AR was 312-fold and 74-fold higher than that of AN and BN, respectively. There was no significant difference in the expression level of RR-2 between AN and BN. The expression levels of RR-1 were extremely low compared with RR-2 and CPG. RR-1 was not detected in BN, but had higher expression in AR and AN, there was no significant difference in the expression level of RR-1 between AR and AN. The expression levels of CPG12-like precursor and PpolCPG24 genes in AR were significantly higher than those in AN and BN. For the rest of unknown cuticular protein genes,the expression level of AR was higher than that of AN and BN. The expression level of cuticular protein genes were different in the AN, BN and AR. It's suggested the caste differentiation was specificity.