Study On The Host Selection And Chemical Communication Mechanism Between Tyrophagus Putrescentiae And Its Mushroom Hosts

Tyrophagus putrescentiae Schrank is one of the most common storage mites with a cosmopolitan occurrence. It carrys pathogenic microorganisms and causes storage mildew,human allergic dermatitis, pulmonary acariasis and intestinal acariasis. It feeds on mycelia and mushroom fruit bodies from the lura of cultivation bags into substrate, however, the effect of chemicals is difficult due to the mite burrow into inner tissues and strong conceal.Its host range, biology and ecology and have been some studied in the world. We found the mite ppreferred some species of mushroom hosts, however, the research on the mechanism of host selection is rare. In this paper, it was investigated that biological characteristics of T.putrescentiae feeding on 9 mushroom hosts, Lentinula edodes (Berk.) Pegler, Pleurotus ostreatus Kumn, P. eryngii var. tuoliensis Mou., P. pulmonarius (Fr.) Quel., Ganoderma lucidum (Leyss. ex Fr. ) Karst., Flammulina velutipes Sing., Agaricus bisporus Lange and Agrocybe cylindracea (Dc. ex Fr.) R Mairel, host prerence, olfactory response on addicted host volatiles and chemical communication mechanism of addicted host selection. The results will reveal the olfaction system of mites, chemical communication mechanism of the mite and its addictecd host, and provide theoretical basis for efficient use of host volatiles as pest biocontrol. The results are summarized as follows:1. Temperature-dependent development and reproductive traits of T. putrescentiae have studied reared on nine different edible mushrooms at 16? to 34?, 80% RH. The growth rate of T. putrescentiae decreased linearly with temperature except L. edodes, but then growth slowly and increased the developmental duration at 34?. Significant differences were observed in immature development, female longevity and fecundity among different mushroom hosts at the same temperature. The mite's sensitive on the temperature is different with the host different, egg and larval stages of the mite are more sensitive period than others. The shortest developmental duration is feeding on F. velutipes,following by P. eryngii var, tuoliensis, A. bisporus,P. ostreatus, P. pulmonarius, A.polytricha and A.cylindracea, the longest duration is feeding on L. eodes and G. lucizVdum.The optimum temperature is 31?. At this temperature, the total developmental duration is from 7.0 ±0.2 d ( feeding on F. velutipes,)?12.3±0.1 d (feeding on G. lucidum).The threshold temperature of different stage of T. putrescentiae is from 7.5? to 14.1?,different with hosts. The maximum fecundity of T. putrescentiae is 212.9 eggs per female feeding on F. velutipes following by A. polytricha. The maximum intrinsic rate of increase(rm) is feeding on F. velutipes and A. polytricha, 3.4 and 3.2, respectively, while the lowest is 2.0 feeding on L. edodes and G. lucidum.2. Host preference of T. putrescentiae is observated using two methods, indoor bioassay and field trapping. The host preference behavior of T. putrescentiae is significantly different among nine mushroom host by indoor bioassay, especially addicted F. velutipes, P.eryngii var. tuoliensis, P. ostreatus and L. edodes. The selective probability of F. velutipes is higher than others, and minimal opportunity to choose G. lucidum observated by four arm olfactometer. Field trapping test also shows that the host preference of T. putrescentiae is significantly different among nine mushroom host (F=15.09; df=8, 26; p<0.0001). The populations of T. putrescentiae is highest feeding on F. velutipes, lowest on G. lucidum.3. The volatile compositions in mycelium (solid and liquid culture), fuitbodies and mycelium infestated by mites of addicted host, F. velutipes, are analysed by solid phase microextraction (SPME) and GC-MS method. The results show that the way of culture,mite damage stress and different development stages can clearly affect the type of secondary metabolites. The content of sesquiterpenes is highest in mycelium stage under solid and liqiud culture, 84.67% and 51.86%, respectively. There are 11 same compounds in two culture ways of mycelium. The content of 2,6-Di-tert-butyl-4-meth -ylphenol is highest on fruitbody stage, 39.75%, and other heterocyclic compounds containing 19.41%. The volatiles are completely different between mites' stress and the normal, however, have one same compound, Cedrol, with the content of 0.84%. ?-Caryophyllene from mycelium,Tridecane from mycelium induced by mites, Benzaldehyde and Pentadecane from non-host volatile attract the mite, T. putrescentiae. However, two alarm pheromones, (Z)-Citral and Neryl formate,one volatile induced by mites,Cedrol,and insect pheromone,?-Pinene,repell the mite. (Z)-Citral may reduce the attractiveness of other compounds analysed by four competition test. These results suggest that ?-Caryophyllene, Benzaldehyde and Pentadecane play an important role in the host selection of T. putrescentiae.4. By analysing the mite's transcriptome, eleven putative OBPs, two putative CSPs,seven putative ORs, one GRs and five IRs are identified using bioinformatics method,named TputOBP1-11, TputCSP1-2, TputORl-7, TputGRl-2 and TputIRl-5. The result of evolutionary analysis discovers that TputOBPs have been characterized into four main subfamilies Classic, Plus-C, Dimer, and ABP?, two TputCSPs shared most homology with highly conserved N-terminal YTTKYDN(V/I)(N/D)(L/V)DEIL and C-terminal KYDP regions. Phylogenetic analysis showed that the evolution of the chemoreceptor genes including ORs, GRs and IRs superfamily are highly dynamic with 5-7 transmembrane structure. We found that the genetic distances between many chemoreceptor genes are too low to be clustered by the neighbor-joining method. No olfactory coreceptor - OR83b-like gene is found in the Acarina, T. putrescentiae and I. scapularis. The ORs of T. putrescentiae were characterized into the seven-transmembrane domain GPCRs superfamily. TputOR3 and six sex pheromone receptors of Bombyx mori Linnaeus are grouped together in a single lineage. TputIR1, 3, and 4 were grouped with IscalRl into IR8a/25a lineage, the function of IR8a and IR25a reported like co-receptors as Orco and ORs; TputIR2 is grouped with DmelIR84a, which was accompanied by a significant odor-specific IR. The function of IR84a was presumed to activate by the fruit odors like Phenylacetic acid and Phenylacetaldehyde, which sensory neurons express the male-specific courtship transcription factor and their activity was required for proper male courtship behavior.5. The 3D structures of TputCSP1 and TputCSP2 are predicted by homology modeling to presume those physiological functions by protein docking with volatiles of F. velutipes.The calculated molecular masses of TputCSP1-2 are 14.9 and 12.1 kDa, respectively. The 3D models revealed that there are six-helices, which in TputCSP1 is roughly globular in shape, but in TputCSP2 is more flabby and bigger bulk. The potential binding characteristics of the two TputCSPs with 19 odourants from host, non-host and alarm pheromone predicted using AutoDock. The results of molecular docking show that(-)-Alloaromadendrene from host volatile, 2-methylnaphthalene from non-host volatile and cyclopentadecane induced by mites are most closely bound, and the three compounds with higher binding capacity with TputCSP1 based on the time series of potential energy and the RMSD of the backbone for a 5 ns MD simulation.However, 19 compounds have higher inhibition constants (k1>10) with TputCSP2 without ideal combination. This research shows that CSPs genes are involved in recognizing, identifying, transporting, signaling chemical factors and stimulating information function of T. putrescentiae and are also involved in host recognition and location.The population dynamics and host selection preference of T. putrescentiae on different mushroom are clearly analytical polyphagous pest those patterns of host utilization. It provides an important theoretical basis of friendly environment comprehensive treatment strategies against the mite. At the same time, the research reveals the interaction of T.putrescentiae with its addicted host by olfactory behavior reaction and chemical communication mechanism, clarify the internal host location mechanism, and provides important theory basis of pest behavior control measures.