Dietary exposure to sulfamethazine,nanoplastics and their binary mixture disrupts the spermatogenesis of marine medaka(Oryzias melastigma)

In the coastal environment,the co-occurrence of antibiotic and nanoplastic pollution is common.Investigating their individual and combined toxicity to marine organisms is of great necessity.In the present study,the reproductive toxicity of sulfamethazine(SMZ)and nanoplastics(polystyrene,PS)via the dietary route on the spermatogenesis of marine medaka(Oryzias melastigma)was examined.After 30 d of dietary exposure,SMZ alone decreased the gonadosomatic index(GSI)value(~35%)and the proportion of undifferentiated type A spermatogonia(A_(und))(~40%),probably by disrupting the testicular sex hormone production,the spermatogenesis-related growth factor network and the balance of apoptosis.Individual exposure to PS did not affect the GSI value or the proportions of germ cells at different developmental stages,but dysregulated the expression of several spermatogenesis-related genes.Interestingly,the presence of PS alleviated the decreased GSI value caused by SMZ.This alleviation effect was achieved by enhancing the spermatogonia differentiation instead of reversing the suppressed self-renewal of A_(und),suggesting that the mixture of PS and SMZ could cause reproductive effects in a different way.These findings expand our knowledge of threats of ubiquitous antibiotic and nanoplastic pollution to fish reproduction and population.

The underlying mechanism of variety–water–nitrogen–stubble damage interactions on yield formation in ratoon rice with low stubble height under mechanized harvesting

Agronomic measures are the key to promote the sustainable development of ratoon rice by reducing the damage from mechanical crushing to the residual stubble of the main crop, thereby mitigating the impact on axillary bud sprouting and yield formation in ratoon rice. This study used widely recommended conventional rice Jiafuzhan and hybrid rice Yongyou 2640 as the test materials to conduct a four-factor block design field experiment in a greenhouse of the experimental farm of Fujian Agricultural and Forestry University, China from 2018 to 2019.The treatments included fertilization and no fertilization, alternate wetting and drying irrigation and continuous water flooding irrigation, and plots with and without artificial crushing damage on the rice stubble. At the same time, a 13C stable isotope in-situ detection technology was used to fertilize the pot experiment. The results showed significant interactions among varieties, water management, nitrogen application and stubble status.Relative to the long-term water flooding treatment, the treatment with sequential application of nitrogen fertilizer coupled with moderate field drought for root-vigor and tiller promotion before and after harvesting of the main crop, significantly improved the effective tillers from low position nodes. This in turn increased the effective panicles per plant and grains per panicle by reducing the influence of artificial crushing damage on rice stubble and achieving a high yield of the regenerated rice. Furthermore, the partitioning of 13C assimilates to the residual stubble and its axillary buds were significantly improved at the mature stage of the main crop, while the translocation rate to roots and rhizosphere soil was reduced at the later growth stage of ratooning season rice. This was triggered by the metabolism of hormones and polyamines at the stem base regulated by the interaction of water and fertilizer at this time. We therefore suggest that to achieve a high yield of ratoon rice with low stubble height under mechanized harvesting, the timely application of nitrogen fertilizer is fundamental,coupled with moderate field drying for root-vigor preservation and tiller promotion before and after the mechanical harvesting of the main crop.

Comparison of short-term toxicity of 14 common phycotoxins(alone and in combination)to the survival of brine shrimp Artemia salina

Toxic harmful algal blooms(HABs)can cause deleterious effects in marine organisms,threatening the stability of marine ecosystems.It is well known that different strains,natural populations and growth conditions of the same toxic algal species may lead to different amount of phycotoxin production and the ensuing toxicity.To fully assess the ecological risk of toxic HABs,it is of great importance to investigate the toxic effects of phycotoxins in marine organisms.In this study,the short-term toxicity of 14 common phycotoxins(alone and in combination)in the marine zooplankton Artemia salina was investigated.The 48 h LC_(50)of the 14 phycotoxins varied from 0.0193µg/mL to 2.415µg/mL.The most potent phycotoxin was azaspiracids-3(AZA3;with a LC_(50)of 0.0193µg/mL),followed by azaspiracids-2(AZA2;0.0226µg/mL),pectenotoxin-2(PTX2;0.0460µg/mL)and dinophysistoxin-1(DTX1;0.0818µg/mL).For the binary exposure,okadaic acid(OA)induced potential additive effects with DTX1,probably due to their similar structure(polyether fatty acid)and mode of action(attacking the serine/threonine phosphoprotein phosphatases).On the other hand,OA showed potential antagonistic effects with PTX2,which might be accounted for by their activation on the detoxification activity of cytochrome P450 activity.In addition,DTX1 induced potential synergetic effects with saxitoxin(STX),yessotoxin(YTX)or PTX2,suggesting the hazard potency of the mixtures of DTX1 and other phycotoxins(like STX,YTX and PTX2)with regard to the ecological risk.These results provide valuable toxicological data for assessing the impact of phycotoxins on marine planktonic species and highlight the potential ecological risk of toxic HABs in marine ecosystems.

Discovery of Cladonema multiramosum sp.nov.(Cnidaria:Hydrozoa:Cladonematidae)using DNA barcoding and life cycle analyses

In contrast to typical planktonic hydromedusae,Cladonema medusae are mostly benthic,with specialised adhesive branches to adhere to the substrate.In this study,a Cladonema species discovered in a laboratory aquarium in Fuzhou,China,was confirmed as a new species,based on morphological and molecular analyses.The species was named Cladonema multiramosum sp.nov.Its medusa is distinct from that of congeners possessing substantially more adhesive branches(8-24,rarely 5-7),and tiny branches on the upper radial canals.The validity of C.multiramosumum sp.nov.was also supported by molecular phylogenetic analyses based on the mitochondrial 16S rDNA sequence.However,C.multiramosum sp.nov.medusa also displayed considerable phenotypic plasticity with respect to its radial canals,tentacles,stinging branches per tentacle,oral tentacles,manubrium,and gonads,hindering species identification based solely on morphology.Although some morphological characteristics of hydroids(filiform tentacles and medusa buds)and nematocysts could also be used as diagnostic characters in the genus Cladonema,this information is unavailable for some Cladonema species.Thus,the taxonomy within the genus Cladonema was re-evaluated based mainly on the morphological characteristics of the medusa.Further revision of the genus Cladonema should be made when supplementary information on the life cycle and DNA barcoding are updated.

The Magnaporthe oryzae effector Avr-PikD suppresses rice immunity by inhibiting an LSD1-like transcriptional activator

Avirulence effectors(Avrs),encoded by plant pathogens,can be recognized by plants harboring the corresponding resistance proteins,thereby initiating effector-triggered immunity(ETI).In susceptible plants,however,Avrs can function as effectors,facilitating infection via effector-triggered susceptibility(ETS).Mechanisms of Avr-mediated ETS remain largely unexplored.Here we report that the Magnaporthe oryzae effector Avr-PikD enters rice cells via the canonical cytoplasmic secretion pathway and suppresses rice basal defense.Avr-PikD interacts with an LSD1-like transcriptional activator AKIP30 of rice,and AKIP30 is also a positive regulator of rice immunity,whereas Avr-PikD impedes its nuclear localization and suppresses its transcriptional activity.In summary,M.oryzae delivers Avr-PikD into rice cells to facilitate ETS by inhibiting AKIP30-mediated transcriptional regulation of immune response against M.oryzae.

Reduced pigmentation and thyroid hormone disruption in zebrafish embryos caused by industrial sludge near Bohai Bay,China

In recent years,pollution caused by the discharge of industrial wastewater into Bohai Bay has posed a potential threat to the health of surrounding residents.Sludge was collected from the outlet of a factory that discharges effluent into Bohai Bay,and alcohol extracts of sludge(SE)were prepared.We confirmed by UPLC-MS/MS analysis that the SE contained PAHs,including fluorene,pyrene,and phenanthrene.Zebrafish embryos as animal models were exposed to 0.1,0.3,0.5,1 and 5 mg/mL SE from 2 to 4 h post-fertilization(hpf)until 120 hpf.The results showed that SE caused a concentration-dependent increase in mortality and a decrease in hatchability.We found that SE significantly reduced eye pigmentation and decreased the movement of embryos and larvae.In addition,SE decreased triiodothyronine(T3)content and down-regulated the mRNA expression of some thyroid hormone-related genes including TPO and Thrβ,and caused the up-regulation of Dio2 and Dio3 at 120 hpf.Exposure to three individual PAHs found in SE,namely fluorene,pyrene,and phenanthrene,caused morphological and transcriptional changes that were similar to those caused by SE exposure.These findings indicate that PAHs in SE can reduce the pigmentation of zebrafish,which may be related to the genetic changes associated with thyroid hormones,and that zebrafish eye pigmentation can be used as an indicator of PAHs exposure.

干旱胁迫下水稻根鞘微生物群落结构

在干旱胁迫条件下,水稻根系表面能形成根鞘以提高其水分利用效率。根鞘中微生物也具有提高水稻抗旱能力的潜在作用,但是目前对干旱胁迫下水稻根鞘中微生物群落的研究还很少。本研究比较了3种条件下(充分灌溉、干旱胁迫Ⅰ和干旱胁迫Ⅱ)的水稻根系性状、根鞘形成和根鞘微生物群落。研究结果表明,灌溉处理显著影响土壤微生物组成和共线性网络。干旱肋迫条件能促进一些有益微生物在根鞘中积累,如镔骨细菌门(Patescibacteria)、马赛菌属(Massilia)、类诺卡氏菌属(Nocardioides)、弗拉特氏菌属(Frateuria)、Angustibacter细菌和篮状菌属(Talaromyces)真菌;此外,干旱也是促进水稻根鞘中有害真菌积累的一个潜在危害因素。这些研究结果表明,根鞘和根鞘微生物都具有提高水稻抗旱性的潜力。在今后的研究中,分离并应用根鞘中的有益微生物,并与科学的灌溉方式相结合,是实现水稻绿色栽培的有效途径之一。