Gnetum is a pantropical distributed gymnosperm genus. As being dioecious, Gnetum species apply female and male strobili to attract and provide nutrition to insect pollinators. Due to its unique gross morphology, a Gnetum male strobilus receives much attention in previous taxonomic and evolutionary studies. However, underlying molecular mechanisms that control male strobilus development and pollination adaptation have not been well studied. In the present study, nine full-length transcriptomes were sequenced from three developmental stages of the G. luofuense male strobili using Oxford Nanopore Technologies. In addition, weighted gene co-expression network analysis (WGCNA), and RT-qPCR analysis were performed. Our results show that a total of 3138 transcription factors and 466 long non-coding RNAs (lncRNAs) were identified, and differentially expressed lncRNAs and TFs reveal a dynamic pattern during the male strobilus development. Our results show that MADS-box and Aux/IAA TFs were differentially expressed at the three developmental stages, suggesting their important roles in the regulation of male strobilus development of G. luofuense. Results of WGCNA analysis and annotation of differentially expressed transcripts corroborate that the male strobilus development of G. luofuense is closely linked to plant hormone changes, photosynthesis, pollination drop secretion and reproductive organ defense. Our results provide a valuable resource for understanding the molecular mechanisms that drive organ evolution and pollination biology in Gnetum.
Abstract A field survey of native herbaceous plants and associated soil in an antimony mining area of Xikuangshan, Hunan Province, China was conducted to identify species that accumulate heavy metals in their tissues. The results indicate that the soils in the mining area were contaminated mainly by As and Sb, at concentrations of 423.77–526.57 and 228.37–445.20 mg/kg, respectively. Of the herbaceous plants, Miscanthus sinensis and Imperata cylindrica exhibited Hg and Cd phytoextraction, with bioconcentration factors (BCFs) and translocation factors (TFs) greater than 1. Moreover, Phytolacca americana could be used for the phytostabilization of Pb and Cd (BCF = 1.06 and 7.66, respectively), and Cynodon dactylon had considerable potential for As and Sb stabilization (BCF = 2.02 and 6.62, respectively). Boehmeria was capable of accumulating Sb and As in its shoots (TF = 3.12 and 4.86, respectively). Additionally, the concentration of Sb in the roots of C. dactylon reached 2209.3 mg/kg, which is the highest Sb concentration reported in a plant species to date. Our data suggest that native herbaceous plants growing in metal‐contaminated sites have phytoremediation potential.
Platycladus orientalis in China has a lifespan of one to several thousands of years. The long lifespans of trees have attracted interest in aging at the molecular level. There is little information on how the global process is controlled. In this study, the MDA content, SOD and POD activities were higher in ancient P. orientalis than in 20-year-old Platycladus orientalis , and the content of protein showed the inverse trend. We obtained 48,044 unigenes having an average length of 896 bp from pooled samples of P. orientalis by transcriptome sequencing. Microarray analysis produced a high-resolution age-course profile of gene expression levels in different age of P. orientalis. In total, 418 differentially expressed genes were identified. The use of highly informative clustering revealed distinct time points at which oxidation reduction and photosynthesis pathways changed. Eight clusters with distinctive expression patterns were identified, the expression of metabolism, photosynthesis, oxidation reduction and transporters related genes were downregulated and protein synthesis, transcription, signal transduction and senescence related genes were upregulated with increasing age. Total chlorophyll, chlorophyll a, and chlorophyll b levels were decreased steadily with age. This study discovery of potential candidate genes affecting photosynthesis in different P. orientalis ages and at senescence, and for identification of the functions of genes involved in regulation of photosynthesis. This work also suggests that improving photosynthetic efficiency under field conditions will require the consideration of multiple factors, such as stress responses.
Soil salinization poses a serious threat to the environment and agricultural productivity worldwide. Studies on the physiological and molecular mechanisms of salinity tolerance in halophytic plants provide valuable information to enhance their salt tolerance. Tangut Nitraria is a widely distributed halophyte in saline-alkali soil in the northern areas of China. In this study, we used a proteomic approach to investigate the molecular pathways of the high salt tolerance of T. Nitraria. We analyzed the changes in biomass, photosynthesis, and redox-related enzyme activities in T. Nitraria leaves from plant seedlings treated with high salt concentration. Comparative proteomic analysis of the leaves revealed that the expression of 71 proteins was significantly altered after salinity treatments of T. Nitraria. These salinity-responsive proteins were mainly involved in photosynthesis, redox homeostasis, stress/defense, carbohydrate and energy metabolism, protein metabolism, signal transduction, and membrane transport. Results showed that the reduction of photosynthesis under salt stress was attributed to the down-regulation of the enzymes and proteins involved in the light reaction and Calvin cycle. Protein-protein interaction analysis revealed that the proteins involved in redox homeostasis, photosynthesis, and energy metabolism constructed two types of response networks to high salt stress. T. Nitraria plants developed diverse mechanisms for scavenging reactive oxygen species (ROS) in their leaves to cope with stress induced by high salinity. This study provides important information regarding the salt tolerance of the halophyte T. Nitraria.
Abstract Background Gnetum is an economically important tropical and subtropical gymnosperm genus with various dietary, industrial and medicinal uses. Many carbohydrates, proteins and fibers accumulate during the ripening of Gnetum seeds. However, the molecular mechanisms related to this process remain unknown. Results We therefore assembled a full-length transcriptome from immature and mature G. luofuense seeds using PacBio sequencing reads. We identified a total of 5726 novel genes, 9061 alternative splicing events, 3551 lncRNAs, 2160 transcription factors, and we found that 8512 genes possessed at least one poly(A) site. In addition, gene expression comparisons of six transcriptomes generated by Illumina sequencing showed that 14,323 genes were differentially expressed from an immature stage to a mature stage with 7891 genes upregulated and 6432 genes downregulated. The expression of 14 differentially expressed transcription factors from the MADS-box, Aux/IAA and bHLH families was validated by qRT-PCR, suggesting that they may have important roles in seed ripening of G. luofuense . Conclusions These findings provide a valuable molecular resource for understanding seed development of gymnosperms.
γ-Aminobutyric acid (GABA) is an important neurotransmitter in mammals whose receptor is reported to be regulated by flavonoids. In plants, it is considered to be at the intersection of carbon and nitrogen metabolism, but its relationship with flavonoid metabolism remains unclear. Our recent RNA-seq analysis showed that expression of flavonoid biosynthetic genes was influenced in poplar by the blockage of α-ketoglutarate dehydrogenase (α-KGDH) activity and the application of GABA under NaCl stress, accompanied by the changes in GABA shunt activity. Here, we further found that the flavonoid accumulation was significantly affected by blocking the activities of α-KGDH and GABA transaminase as well as applying exogenous GABA, coupled with the changes of endogenous GABA contents. Key genes involved in the flavonoid biosynthetic pathway were also significantly influenced, including two PALs, 4CL, and two CHSs. Our results suggest that the GABA shunt is closely associated with the metabolism of flavonoids, which would benefit future understanding of GABA's roles in carbon allocation by regulating the pathway of flavonoid biosynthesis under normal or stress conditions.
The decay of animal corpses may release various nutrients into the surrounding environment and participate in the biogeochemical cycle. However, few studies have involved the sulphur cycle in animal corpse decay. Here, we conducted an indoor control experiment at five different temperature gradients (23, 26, 29, 32 and 35 °C) to explore the change of sulphur cycling microbes and genes under corpse decay by metagenomic sequencing, metagenomic binning, and 16S rRNA sequencing. Our results showed that total sulphur content decreased by 41.82% due to decomposition. The dominant phyla of the S-cycle microbes were Proteobacteria, followed by Bacteroidetes and Acidobacteria. Corpse decay decreased the pathways involved in assimilatory sulphate reduction, sulfur oxidizing (Sox) system, organic sulphur transformation, and sulphur oxidation pathway, but increased the links between inorganic and organic sulphur transformation. The alpha diversity of sulphur cycling genes decreased with increasing temperature and the deterministic process was dominant in most of temperature gradients. The diversity of microbial community was the main driving factors of sulphur cycling genes, followed by corpse decay and temperature. We obtained 257 high-quality metagenome assembled genomes (MAGs) containing sulphur cycling genes, and the results of metagenome-assembled genomes provide evidence for the covariation of sulphur cycling genes, such as sir, cysD, cysH, and ssuC, which shared the function of assimilatory sulphate reduction. Our research reveals the pathways of microbial sulphur cycling and contributes to the understanding of the elemental cycle associated with animal corpse decay.
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