| Caste plasticity and polymorphism in developmental pathways are remarkable characteristics of termite societies.In Reticulitermes,workers are characterized by unique flexibility,a worker can develop in one of three ways:via moults into higher instar wokers,via two successive moults into sterile soldiers,or via a single moult into apterous neotenic reproductive in the absence of or at a great distance from the reproductive to provide for continued or additional growth of the colony.Up to now,nobody suspects that nymphs develop into neotenic or primary reproductives by one moults and workers are able to develop into neotenic reproductive by one moult.Is it true that the workers can transform into neotenic reproductive by a single moult?Actually,the developmental pathways of workers into neotenic reproductive remains unknown or unclear.At present,morphological characteristics,the development of the gonads,cell apoptosis during oogenesis and gene expressions were investigated during the female workers of Reticulitermes labralis transform into neotenic reproductives.The main results describe as follows:1.We identify for the first time that the female workers of R.labralis develop into neotenic reproductive after a pre-NR stage,indicating that a female worker become a NR through two successive moults:via one moult into female pre-NRs,the female pre-NRs into NRs via one moult.This finding showed that the female pre-NRs was a single transitional instar during the development from workers to NRs,and the individual development at each stage exhibited specific morphological characters.The difference in morphology among the female workers,pre-NRs and NRs was significant.The length of abdomens significantly increased from the female workers(0.7±0.04 mm)moulting into NRs(1.73±0.09 mm),whereas there was no significant difference between pre-NRs(1.63±0.02mm)into NRs.The seventh sternites of the female NRs was longer compared with the female workers.There was significant difference in the length of seventh stemites between NRs(0.5±0.01 mm),pre-NRs(0.38±0.025 mm)and workers(0.24 mm±0.02).These results show the development of the female workers transform into NRs more clearly,and provide morphology basis for potential reproductive capacity of female workers.2.The starting point for oogenesis resumption during development of the workers into NRs,and the starting point for ovaries growth during development of the workers into pre-NRs,whereas the male workers copulated directly with queens without undergoing any moults.Although the size of ovaries of pre-NRs significantly increase compared with that of wokers,the non-activated oocytes were still suppressed by degenerate follicle cells.The degenerate follicle cell is a leading cause of reduced fertility in pre-NRs,pre-NRs is a transitional type during development of the female worker to NR caste.After the female workers developed into pre-NRs,the oocytes were still surround by elongated follicle cells.After developed into NRs,the follicle cells have a remarkable recovery from degradation.The mean size of the ovaries had a greater growth after the workers(0.7±0.04 mm)developed into pre-NRs(1.63±0.02 mm),but did not increase significantly after the pre-NRs into NRs(1.73±0.09 mm).The mean size of oocytes significantly increased from the female pre-NRs(25.06±5.8 ?m)moulting into NRs(69.55±4.8 ?m),whereas there was no significant difference between workers(22.83±4.2?m)into pre-NRs.This results provide cytological and histological basis for potential reproductive capacity of female workers.3.In the workers,the oocyte development is inhibited by degenerated follicle cells instead of all oocytes dying by apoptosis,which lead to female workers retaining full reproductive potential.Although the follicles of the workers are degenerate,none of the oocytes and follicle cells undergoes.The majority of the stained nuclei were located in the germarium region of ovarioles which contained the oogonia.The oogonia of NRs exhibited the lowest apoptotic rate compared with those of the workers and pre-NRs.Indicating that the ovaries start to increase the number of oogonia after the workers moult to pre-NRs.Only oocytes and follicle cells which surrounded oocytes in the NRs were TUNEL-positive.Demonstrate that the starting point for oogenesis resumption during development of the workers into pre-NRs.This result show cause of the female workers retaining full reproductive potential,and provide evidence on the study of special reproductive mechanism of other caste.4.We performed qRT-PCR analysis of the 7 genes involved to oocyte meiosis in the workers,pre-NRs and NRs,and demonstrate that the starting point for oocyte meiosis resumption during development of the pre-NRs into NRs.Pre-NR type is a transitional type during development in oocyte meiosis resumption of the female worker to NRs caste.There is 2 genes are expressed in higher levels in NRs than in workers and pre-NRs.We demonstrated that cyclin dependent kinase 1 gene?G2/mitotic-specific cyclin-B3-like gene and G2/mitotic-specific cyclin-A-like gene which control MPF were expressed in higher levels in NRs than in workers and pre-NRs.The transcription level of NRs was 31-fold,94-fold and 36.3-fold higher than that of pre-NRs,it was 68.3-fold,25.2-fold and 98.4-fold higher than that of workers,respectively.Aurora kinase A-like gene and Serine/threonine-protein kinase polo gene were expressed in higher levels in NRs than in workers and pre-NRs.The transcription level of Aurora kinase A-like gene and Serine/threonine-protein kinase polo gene of NRs was 57.7-fold and 106.2-fold higher than that of pre-NRs,it was 130.7-fold and 158.8-fold higher than that of workers,respectively.Cell division cycle protein 20 homolog gene were expressed in higher levels in NRs than in workers and pre-NRs.The transcription level of NRs was 62.7-fold higher than that of pre-NRs,it was 64.2-fold higher than that of workers,respectively.Anaphase-promoting complex subunit CDC26 isoform X1 gene were expressed in higher levels in NRs than in workers and pre-NRs.The transcription level of NRs was 2.5-fold higher than that of pre-NRs,it was 4.6-fold higher than that of workers,respectively.There was significant difference in the expression level of Anaphase-promoting complex subunit CDC26 isoform X1 between NRs,pre-NRs and workers.This data show re-NR type is a transitional type during development in oocyte meiosis resumption of the female worker.to NR caste.These results show the genes expressed oocyte meiosis development,and provide evidence for the relationship between oocyte meiosis development and caste differentiation... |
PDF Full Text Request