| C. elegans is an animal living in soil with simple structure and transparent body, and thus it is thought as an ideal model for the biological studies. C. elegans lives in a very complex environment where exists a variety of stimulations such as pathogen, odor, food, osmotic pressure and pH et al. C. elegans also has a subtle chemosystem that can recognize those stimulations efficiently. Also depending on its sensitive olfactory system, C. elegans can search bacterial food in the soil. At the same time, because there are some odors that attract the worms inherently but cannot provide nutrition for them, they have to employ the strategy of adaption to ignore these odors. That is to say, olfactory adaptation is important for C. elegans to search food.The forming of olfaction as well as the olfactory adaption in C.elegans involves the G protein signaling pathway. In this pathway, the chemical molecules of odors bind to the G protein coupled receptor (GPCR), then G protein a submit (Ga) is dissociated from the trimetric proteins and is activated, and finally stimulate the downstream cascades. But in the olfactory adaption, the persistent stimulation of odors also triggers EGL-4 to accumulate within the nucleus of AWC sensory neuron, and then leads to the changes of a variety of downstream genes. Additionally, some other researchers in this field still consider that some other potential pathways may exist to regulate the calcium influxes and DAG level directly instead of via EGL-4. So, we designed to investigate if some novel pathways, including some other Gas regulate olfactory adaptation in C. elegans. The results of this paper are as follows:1. gpa-7 and gpa-13 are involved in the olfactory adaptation to benzaldehyde of C. elegans. We found that gpa-7 and gpa-13 mutant animals are defective in olfactory adaptation to benzaldehyde by testing Ga mutant animals. After we achieved the complementary expression of gpa-7 and gpa-13 and tested their olfactory adaptation phenotype to benzaldehyde, it was found that the complementary expression of gpa-7 and gpa-13 rescued the defect of adaption, suggesting that both of them really involved in regulating the olfactory adaptation to benzaldehyde.2. The identification of the genes downstream of gpa-7 and gpa-13. Combined the methods of RNAi and mutants screening, we tried to identify the genes downstream of gpa-7 and gpa-13. Our results showed that the key genes kin-2 and unc-13 in cAMP pathway, as well as the key genes pde-1, plc-1, and pkc-1 in PLC pathway had no effects on the olfactory adaption for benzaldehyde in C. elegans. Contrarily, the mutation of genes daf-11 and tax-4 in cGMP pathway significantly effected the formation of olfaction for benzaldehyde in C. elegans.3. To investigate if DAG signaling pathway participate in the defects of olfactory adaption of gpa-7 and gpa-13. To investigate if gpa-7 and gpa-13 regulate olfactory adaptation though a previously reported DAG signaling pathway, we detected the mRNA level of dgk-1, dgk-3 and egl-30 that are key genes of DAG signaling pathway using RT-PCR. Through analyzing the results, it was suggested that the mutant of gpa-7 increased DAG level, thus led to the defect of olfactory adaptation. But gpa-13 seemed not to regulate olfactory adaptation through DAG signaling pathway. Meanwhile, we also tested the olfactory adaptation of gpa-7 and gpa-13 with the treatment of the antagonist of DAG (HAG). However, the addition of HAG could not rescue the defect of olfactory adaptation of gpa-7 and gpa-13 mutant animals. Therefore, the relationship between gpa-7 and DAG should be further elucidated by some other experiments.Innovation of my current investigation includes as follows:The two novel Ga GPA-7 and GPA-13 have been suggested to be involved in the olfactory adaptation to benzaldehyde of C. elegans. |
PDF Full Text Request