Neuropeptide Y receptor Y8b(npy8br)regulates feeding and digestion in Japanese medaka(Oryzias latipes)larvae:evidence from gene knockout

Neuropeptide Y receptor Y8(NPY8R)is a fish-specific receptor with two subtypes,NPY8AR and NPY8BR.Changes in expression levels during physiological processes or in vivo regulation after ventricular injection suggest that NPY8BR plays an important role in feeding regulation;this has been found in only a few fish,at present.In order to better understand the physiological function of npy8br,especially in digestion,we used clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated protein 9(Cas9)technology to generate npy8br-/-japanese medaka(Oryzias latipes).We found that the deletion of npy8br in medaka larvae affected their feeding and digestion ability,ultimately affecting their growth.Specifically,npy8br deficiency in medaka larvae resulted in decreased feed intake and decreased expression levels of orexigenic genes(npy and agrp).npy8br-/-medaka larvae fed for 10 d(10th day of feeding)still had incompletely digested brine shrimp(Artemia nauplii)in the digestive tract 8 h after feeding,the messenger RNA(mRNA)expression levels of digestion-related genes(amy,lpl,ctra,and ctrb)were significantly decreased,and the activity of amylase,trypsin,and lipase also significantly decreased.The deletion of npy8br in medaka larvae inhibited the growth and significantly decreased the expression of growth-related genes(gh and igf1).Hematoxylin and eosin(H&E)sections of intestinal tissue showed that npy8br-/-medaka larvae had damaged intestine,thinned intestinal wall,and shortened intestinal villi.So far,this is the first npy8br gene knockout model established in fish and the first demonstration that npy8br plays an important role in digestion.

Efficacy and biosafety assessment of neuropeptide CAPA analogues against the peach-potato aphid (Myzus persicae)

Insect CAPA neuropeptidesare considered to affect water and ion balance by mediating the physiological metabolism activities of the Malpighian tubules.In previous studies,the CAPA-PK analogue 1895(2Abf-Suc-FGPRLamide)was reported to decrease aphid fitness when administered through microinjection or via topical application.However,a further statistically significant decrease in the fitness of aphids and an increased mortality could not be established with pairwise combinations of 1895 with other CAPA analogue.In this study,we assessed the topical application of new combinations of 1895 with five CAPA-PVK analogues on the fitness of aphids.We found that 1895 and CAPA-PVK analogue 2315(ASG-[β3L]-VAFPRVamide)was statistically the most effective combination to control the peach potato aphid Myzus persicae nymphs via topical application,leading to 72%mortality.Additionally,the combination(1895+2315)was evaluated against a selection of beneficial insects,that is,a pollinator(Bombus terrestris)and three natural enemies(Chrysoperla carnea,Nasonia vitripennis,and Adalia bipunctata).We found no significant influence on food intake,weight increase,and survival for the pollinator and the three representative natural enemies.These results could facilitate to further establish and generate CAPA analogues as alternatives to broad spectrum and less friendly insecticides.