Depletion of stearoyl-CoA desaturase(scd) leads to fatty liver disease and defective mating behavior in zebrafish

Stearyl coenzyme A desaturase(SCD), also known as delta-9 desaturase, catalyzes the rate-limiting step in the formation of monounsaturated fatty acids.In mammals, depletion or inhibition of SCD activity generally leads to a decrease in triglycerides and cholesteryl esters. However, the endogenous role of scd in teleost fish remains unknown. Here, we generated a zebrafish scd mutant(scd-/-) to elucidate the role of scd in lipid metabolism and sexual development. Gas chromatography-mass spectrometry(GC-MS) showed that the scd-/- mutants had increased levels of saturated fatty acids C16:0 and C18:0, and decreased levels of monounsaturated fatty acids C16:1 and C18:1. The mutant fish displayed a short stature and an enlarged abdomen during development. Unlike Scd-/ -mammals, the scd-/- zebrafish showed significantly increased fat accumulation in the whole body,especially in the liver, leading to hepatic mitochondrial dysfunction and severe cell apoptosis.Mechanistically, srebf1, a gene encoding a transcriptional activator related to adipogenesis,acc1 and acaca, genes involved in fatty acid synthesis, and dgat2, a key gene involved in triglyceride synthesis, were significantly upregulated in mutant livers to activate fatty acid biosynthesis and adipogenesis. The scd-/- males exhibited defective natural mating behavior due to defective genital papillae but possessed functional mature sperm. All defects in the scd-/- mutants could be rescued by ubiquitous transgenic overexpression of scd. In conclusion, our study demonstrates that scd is indispensable for maintaining lipid homeostasis and development of secondary sexual characteristics in zebrafish.

Response of Vegetation Cover Change to Drought at Different Time-scales in the Beijing-Tianjin Sandstorm Source Region,China

Dominated by an arid and semiarid continental climate,the Beijing-Tianjin Sandstorm Source Region(BTSSR)is a typical ecologically fragile region with frequently occurring droughts.To provide information for regional vegetation protection and drought prevention,we assessed the relations between vegetation cover change(measured by the Normalized Difference Vegetation Index,NDVI)and the Standardized Precipitation Evapotranspiration Index(SPEI)at different time-scales,in different growth stages,in different subregions and for different vegetation types based on the Pearson's correlation coefficient in the BTSSR from 2000 to 2017.Results showed that 88.19%of the vegetated areas experienced increased NDVI in the growing season;48.3%of the vegetated areas experi-enced significantly increased NDVI(P<0.05)and were mainly in the south of the BTSSR.During the growing season,a wetter climate contributed to the increased vegetation cover from 2000 to 2017,and NDVI anomalies were closely related to SPEI.The maximum correlation coefficient in the growing season(Rmax)was significantly positive(P<0.05)in 97.84%of the total vegetated areas.In the vegetated areas with significantly positive Rmax,pixels with short time-scales(1-3 mon)accounted for the largest proportion(33.9%).The sensitivity of vegetation to the impact of drought rose first and then decreased in the growing season,with a peak in July.Compared with two subregions in the south,subregions in the north of the BTSSR were more sensitive to the impacts of drought variations,especially in the Xilingol Plateau and Wuzhumuqin Basin.All four major vegetation types were sensitive to the effects of drought variations,especially grasslands.The time-scales of the most impacting droughts varied with growth stages,regions,and vegetation types.These results can help us understand the relations between vegetation and droughts,which are important for ecological restoration and drought prevention.

Zinc-finger protein GmZF351 improves both salt and drought stress tolerance in soybean

Abiotic stress is one of the most important factors reducing soybean yield. It is essential to identify regulatory factors contributing to stress responses.A previous study found that the tandem CCCH zincfinger protein Gm ZF351 is an oil level regulator. In this study, we discovered that the Gm ZF351 gene is induced by stress and that the overexpression of Gm ZF351 confers stress tolerance to transgenic soybean. Gm ZF351 directly regulates the expression of Gm CIPK9 and Gm SnRK, leading to stomata closing, by binding to their promoter regions, which carry two CT(G/C)(T/A)AA elements.Stress induction of Gm ZF351 is mediated through reduction in the H3K27me3 level at the Gm ZF351locus.TwoJMJ30-demethylase-likegenes,Gm JMJ30-1 and Gm JMJ30-2, are involved in this demethylationprocess.Overexpressionof Gm JMJ30-1/2 in transgenic hairy roots enhances Gm ZF351 expression mediated by histone demethylation and confers stress tolerance to soybean.Yield-related agronomic traits were evaluated in stable Gm ZF351-transgenic plants under mild drought stress conditions. Our study reveals a new mode of Gm JMJ30-Gm ZF351 action in stress tolerance, in addition to that of Gm ZF351 in oil accumulation. Manipulation of the components in this pathway is expected to improve soybean traits and adaptation under unfavorable environments.

Mobile ARGONAUTE 1d binds 22-nt miRNAs to generate phasiRNAs important for low-temperature male fertility in rice

Phased small interfering RNAs(phasiRNAs) are abundantly expressed in anthers and linked to environment-related male fertility in grasses, yet how they function under different environmental conditions remains unclear. Here, we identified a rice(Oryza sativa) low temperature-induced Argonaute(AGO) protein, OsAGO1d, that is responsible for generating phasiRNAs and preserving male fertility at low temperature. Loss of OsAGO1d function causes low-temperature male sterility associated with delayed programmed cell death of tapetal cells during anther development. OsAGO1d binds miR2118 and miR2275 family members and triggers phasiRNA biogenesis;it also binds 21-nt phasiRNAs with a 5′ terminal U. In total, phasiRNAs from 972loci are OsAGO1d-dependent. OsAGO1d protein moves from anther wall cells into meiocytes, where it loads miR2275 to produce 24-nt phasiRNAs. Together, our results show that OsAGO1d acts as a mobile signal to fine-tune phasiRNA production and this function is important for male fertility at low temperature.

The rice histone methylation regulates hub species of the root microbiota

Plants have a close relationship with their root microbiota,which comprises a complex microbial network.Histone methylation is an important epigenetic modification influencing multiple plant traits;however,little is known about the role of plant histone methylation in the assembly and network structure of the root microbiota.In this study,we established that the rice(Oryza sativa)histone methylation regulates the structure and composition of the root microbiota,especially the hub species in the microbial network.DJjmj703(defective in histone H3K4 demethylation)and ZH11-sdg714(defective in H3K9 methylation)showed significant different root microbiota compared with the corresponding wild types at the phylum and family levels,with a consistent increase in the abundance of Betaproteobacteria and a decrease in the Firmicutes.In the root microbial network,35 of 44 hub species in the top 10 modules in the tested field were regulated by at least one histone methylation-related gene.These observations establish that the rice histone methylation plays a pivotal role in regulating the assembly of the root microbiota,providing insights into the links between plant epigenetic regulation and root microbiota.