Haemaphysalis longicornis는 사람과 동물에게 여러 심각한 병원체를 전달하는 주요 매개체로, 한반도에 널리 분포하고 있다. H. longicornis는 Rickettsia spp., Borrelia spp., Francisella spp., Coxiella spp., 그리고 중증열성혈소판 감소증후군 바이러스 (SFTS virus) 등을 매개하는 것으로 알려져 있다. 국내에 서식하는 H. longicornis의 미생물 군집과 관련된 연구는 많이 진행되지 않은 것으로 확인되었다. 이 연구는 한반도 내 다양한 지역에서 채집된 H. longicornis의 미생물군집 다양성을 지역별, 성장 단계 및 성별에 따라 분석하였다. 2019년 6월부터 7월까지 질병관리청 권역별기후변화매개체감시거점센터 16개 지역에서 채집한 H. longicornis의 16S rRNA 유전자 V3-V4 영역을 PCR로 증폭 후 Illumina MiSeq 플랫폼으로 시퀀싱하였다. Qiime2를 활용한 미생물 다양성 분석을 통해 총 46개의 샘플에서 1,754,418개의 non-chimeric reads를 얻었으며, 평균 126개 의 operating taxonmic unit (OTU) 을 식별하여 총 1,398개의 OTU를 확인하였다. 대부분의 지역에서 Coxiella spp.가 우점종으로 나타났으며, 특히 Coxiella endosymbiont는 가장 높은 우점도를 보이며, Coxiella burnetii와 계통 발생 학적으로 유사한 것으로 확인되었다. 이 연구를 통해 분석된 결과는 각 지역의 H. longicornis 미생물군집 데이터 베이스 구축에 활용되었으며, 이를 통해 지역별 미생물군집의 특이성을 식별할 수 있게 하였다. 이는 한반도의 H. longicornis에 의한 질병 전파 연구와 이를 통한 공중보건 개선에 기여할 것으로 기대된다.

Neurokinin B (NKB) and neurokinin B related peptide (NKBRP) belong to tachykinin peptide family. They act as a neurotransmitter and/or neuromodulator. Mutation of NKB and/or its cognate receptor, NK3R resulted in hypogonadotropic hypogonadism in mammals, implying a strong involvement of NKB/NK3R system in controlling mammalian reproduction. Teleosts possess NKBRP as well as NKB, but their roles in fish reproduction need to be clarified. In this study, NKB and NKBRP coding gene (tac3) was cloned from Nile tilapia and sequenced. Based on the sequence, Nile tilapia NKB and NKBRP peptide were synthesized and their biological potencies were tested in vitro pituitary culture. The synthetic NKBRP showed direct inhibitory effect on the expression of GTH subunits at the pituitary level. This inhibitory effect was confirmed in vivo by means of intraperitoneal (ip) injection of synthetic NKB and NKBRP to mature female tilapia (20 pmol/g body weight [BW]). Both NKB and NKBRP had no effect on the plasma level of sex steroids, E2 and 11-KT. However, NKBRP caused declines of expression level of GnRH I, Kiss2 and tac3 mRNAs in the brain while NKB seemed to have no distinct effect. These results indicate some inhibitory roles of NKBRP in reproduction of mature female Nile tilapia, although their exact functions are not clear at the moment.

Gonadotropin-inhibitory hormone (GnIH) has been found to inhibit the synthesis and release of gonadotropin (GTH) in avian and mammalian species. It was originally identified in the brain of a quail as a novel hypothalamic neuropeptide with a C-terminal Arg-Phe-NH2 motif (RFamide peptide). Homologs of this peptide have been identified in a couple of model fish species such as goldfish (Carassius auratus) and zebrafish (Danio rerio). Understanding GnIH system could be particularly useful in some aquaculture species with problems of frequent reproduction and/or precautious sexual maturation. However, GnIH system in such species has not been studied yet. In this study, we have identified a pupative GnIH gene in the Nile tilapia (Oreochromis niloticus). We also investigated the role of GnIH in the reproduction of this species. The full length sequence of putative tilapia GnIH gene coded for a protein (197 amino acids) containing two modified RFamides (MPLRF and LSQRF) and a LPQRF cDNA sequence of 594 bp. This putative GnIH gene showed high homology with the GnIH genes of Takifugu rubripes (72%) and Tetraodon nigroviridis (74%). PCR analysis showed that expression of this gene was ubiquitously distributed in the whole brain, ovary and testis as well as in the peripheral tissues examined in this study (liver, kidney, intestine, spleen, muscle and gill) except heart and eye. Expression level of this gene in sexually inactive group was significantly higher than the expression level in first gonadal development and sexually active groups (P<0.05). On the contrary, the expression level of LH-β gene was low in sexually inactive group but significantly higher in first gonadal development and sexually active groups (P<0.05). However, no significant difference was observed in the level of FSH-β gene expression between different reproductive phases in this species. In vitro studies revealed an inhibitory effect of GnIH on LH-β mRNA and FSH-β mRNA levels. No significant difference between GnIH and GnIH with LHRH-a treatments on LH-β and FSH-β mRNA expression in female tilapia pituitary cells.

Geneally, rice seeds regardless indica or japonica are showing low germination ratio or completely lost germination ability together with lost of good eating quality under high temperature and humidity conditions. Thus, this study was designed to evaluate a longevity for conservation of good eating quality during long term storage in rice. For the longevity evaluation, germination ability was studied after 5 days of high temperature and humidity stress (50℃/RH 95%). Dharial, originated from Bangladesh and showing weedy type with red pericarp, was selected as a good donor for longevity genes. A mutant was developed from Dharial through EMS mutagenesis and two populations of Dharial/4*Ilmibyeo and Dharial/4*Gopumbyeo were also developed for genetic study. In the 2-DE analysis followed by MALDI-TOF MS with wild and mutant lines, several candidate genes were identified. In the longevity test of two populations, a few lines showing good germination ability after high temperature and humidity stress were selected and subjected to confirm the relationships between longevity and conservation of good eating quality under long term storage.

Fish reproduction is influenced by various external environmental factors. Among these factors, changes of photic conditions are thought be most closely related to the reproduction of many fish species. In recent studies, melatonin that mediates the changes of photic condition outside has been used in an attempt to get a similar effect to photoperiod manipulation without changing photoperiod. However, the effects of exogenous melatonin vary depending on life stages. We have previously investigated the effect of melatonin on reproductive activity in mature Nile tilapia (Oreochromis niloticus). In this study, effects of exogenous melatonin on the spawning activity, the rate of mouth brooding success rate and early survival rate of lavae produced from melatonin treated Nile tilapia were investigated. Nile tilapia at the time of puberty were randomly divided into three groups and fed on control (0 ㎍/g), low-dose melatonin (2.5 ㎍/g BW) or high-dose melatonin (25 ㎍/g BW) diet. Fish were reared indoor tanks at 27～28℃ under natural-photoperiod and fed twice a day at 10:00 and16:00 during the experiment (120 days). Fish were sampled to examine growth and gonadal development on Day 30, 60, 90 and 120. There were no significant differences of somatic growth between control (no melatonin) and melatonin-treated groups, indicating that melatonin administration did not cause any negative effects on the growth of experimental fish. The patterns of gonadal development were almost the same between control and melatonin-treated groups. In juvenile tilapia, treatment with low-dose melatonin resulted in the increase of spawning rate, the rate of mouth brooding success and early survival rate of laval tilapia. However, high-dose melatonin resulted in the decrease of spawning rate, the rate of mouth brooding success and early survival rate of laval tilapia, although the earliest spawning occurred in one of the high-dose group fish. Fish in high-dose melatonin group failed to recover from reproductively suppressed state even after the cease of melatonin treatment, indicating that too much melatonin might act negatively on spawning activities and gonadal maturation in Nile tilapia. In conclusion, the results from this study suggest the possibility that a pertinent dose of melatonin treatment can effectively accelerate the spawning rate and the rate of mouth brooding success, and bring positive effects on early survival rate of tilapia lavae.