Characterization of SlBAG Genes from Solanum lycopersicum and Its Function in Response to Dark-Induced Leaf Senescence

The Bcl-2-associated athanogene (BAG) family is a group of evolutionarily conserved cochaperones involved in diverse cellular functions. Here, ten putative SlBAG genes were identified in tomato. SlBAG2 and SlBAG5b have the same gene structure and conserved domains, along with highly similar identity to their homologs in Arabidopsis thaliana, Oryza sativa, and Triticum aestivum. The qPCR data showed that BAG2 and BAG5b were highly expressed in stems and flowers. Moreover, both genes were differentially expressed under diverse abiotic stimuli, including cold stress, heat stress, salt treatment, and UV irradiation, and treatments with phytohormones, namely, ABA, SA, MeJA, and ETH. Subcellular localization showed that SlBAG2 and SlBAG5b were located in the cell membrane and nucleus. To elucidate the functions in leaf senescence of BAG2 and BAG5b, the full-length CDSs of BAG2 and BAG5b were cloned, and transgenic tomatoes were developed. Compared with WT plants, those overexpressing BAG2 and BAG5b had significantly increased chlorophyll contents, chlorophyll fluorescence parameters and photosynthetic rates but obviously decreased ROS levels, chlorophyll degradation and leaf senescence related gene expression under dark stress. Conclusively, overexpression SlBAG2 and SlBAG5b could improve the tolerance of tomato leaves to dark stress and delay leaf senescence.

Square–torsion gravity, dark matter halos and the baryonic Tully–Fisher relation

Square–torsion gravity is applied to the long standing dark matter problem. In this context the theory reduces to General Relativity complemented by a dark stress–energy tensor due to the torsion of spacetime and is studied under the simplifying assumption of spherical symmetry. The dark stress–energy tensor satisfies an anisotropic structure equation. In vacuum this is equivalent to a wave equation with sources. A natural class of exact solutions is found which explicitly perturbs any seed spacetime metric by a conformal factor. This leads to the concept of dark coating. Static solutions are then used to construct structures that model dark matter halos surrounding baryonic bodies. In the Newtonian régime the baryonic mass $$m_b$$ m b and the flat rotation curve velocity $$v_f$$ v f are related by the baryonic Tully–Fisher relation$$m_b\propto v_f^4$$ m b ∝ v f 4 , a hitherto purely empirical result. The example of a dark halo on the Schwarzschild geometry is made as a toy model for a galaxy. Qualitative an quantitative features of galactic rotation curves are recovered. In this setting, a boundary of staticity is found, called torsion sphere, placed between the photon sphere and the event horizon. The phenomenon of dark radiation is briefly exposed.

Integrated analyses of rice dark response and leaf color regulation reveal links with porphyrin and chlorophyll metabolism

Background Light is a key regulatory signal for rice growth and development. Under dark stress, rice shows leaf yellowing. Whole genome transcriptomic analysis will identify differentially expressed genes (DEG) in dark-treated rice seedlings and DEG-enriched metabolic pathways. Rice leaf color is an essential agronomic trait. Traditional genetic experiments have reported over a hundred of leaf color-related (LCR) genes and some of them were also regulated by light signal. Thus, an integrated analysis for the two set of data will be helpful for illustration of the mechanism for both dark-response and leaf color regulation. Results Transcriptome changes in response to dark treatment were surveyed by RNA-Seq analysis. About 13,115 DEGs were identified. One hundred and fifty rice LCR genes were collected. It was found that 102 LCR genes (68.0%) were also dark-response DEGs, which suggests an overlap between dark response and LCR networks. Fifty DEG overlapped LCR genes was associated with chloroplast development. KEGG analysis revealed enrichment of LCR genes in porphyrin and chlorophyll metabolism (PCM) (18/44, 40.9%). Of the 18 LCR genes in the PCM pathway, 15 were dark-response DEGs (83.3%). More interestingly, most of them are involved in a central PCM sub-pathway, chlorophyll biosynthesis. Conclusions Integrated analysis for dark stress-response and leaf color regulation identified the correlation between the two processes and mutually supported evidences were obtained. It was found that PCM pathway, particularly chlorophyll biosynthesis process, is a core component of the overlap and plays important roles in rice LCR and dark stress-response. This study provides important clues for identifying additional LCR genes, understanding the mechanisms of dark response and leaf color regulation.

Integrated analyses of rice dark response and leaf color control reveal links with porphyrin and chlorophyll metabolism

Background: Light is a key regulatory signal for rice growth and development. Under dark stress, rice shows leaf yellowing. Whole genome transcriptomic analysis will identify differentially expressed genes (DEG) in dark-treated rice seedlings and DEG-enriched metabolic pathways. Rice leaf color is an essential agronomic trait. Traditional genetic experiments have reported over a hundred of leaf color control (LCC) genes and some of them were also regulated by light signal. Thus, an integrated analysis for the two set of data will be helpful for illustration of the mechanism for both dark-response and leaf color control.Results: Transcriptome changes in response to dark treatment were surveyed by RNA-Seq analysis. About 13,115 differentially expressed genes (DEGs) were identified. One hundred and fifty rice LCC genes were collected. It was found that 102 LCC genes (68.0%) were also dark-response DEGs, which suggests an overlap between dark response and LCC networks. Fifty DEG overlapped LCC genes was associated with chloroplast development. KEGG analysis revealed enrichment of LCC genes in porphyrin and chlorophyll metabolism (PCM) (18/44, 40.9%). Of the 18 LCC genes in the PCM pathway, 15 were dark-response DEGs (83.3%). More interestingly, all of them are involved in a central PCM sub-pathway, chlorophyll biosynthesis.Conclusions: Integrated analysis for dark stress-response and leaf color control identified the correlation between the two processes and mutually supported evidences were obtained. It was found that PCM pathway, particularly chlorophyll biosynthesis process, plays important roles in rice LCC and dark stress-response. This study provides important clues for understanding the mechanisms of dark response and leaf color control and identifying additional LCC genes.

RNA degradomes reveal substrates and importance for dark and nitrogen stress responses of Arabidopsis XRN4

XRN4, the plant cytoplasmic homolog of yeast and metazoan XRN1, catalyzes exoribonucleolytic degradation of uncapped mRNAs from the 5′ end. Most studies of cytoplasmic XRN substrates have focused on polyadenylated transcripts, although many substrates are likely first deadenylated. Here, we report the global investigation of XRN4 substrates in both polyadenylated and nonpolyadenylated RNA to better understand the impact of the enzyme in Arabidopsis. RNA degradome analysis demonstrated that xrn4 mutants overaccumulate many more decapped deadenylated intermediates than those that are polyadenylated. Among these XRN4 substrates that have 5′ ends precisely at cap sites, those associated with photosynthesis, nitrogen responses and auxin responses were enriched. Moreover, xrn4 was found to be defective in the dark stress response and lateral root growth during N resupply, demonstrating that XRN4 is required during both processes. XRN4 also contributes to nonsense-mediated decay (NMD) and xrn4 accumulates 3′ fragments of select NMD targets, despite the lack of the metazoan endoribonuclease SMG6 in plants. Beyond demonstrating that XRN4 is a major player in multiple decay pathways, this study identified intriguing molecular impacts of the enzyme, including those that led to new insights about mRNA decay and discovery of functional contributions at the whole-plant level.

Marine Macroalgae: Prospective Hitchhikers of Ship Ballast

Invasive alien species, on successful establishment, can displace native species. The threat of invasive species arises in view of their ability to outcompete and destabilize native biodiversity. Invasive species are found across all taxonomic groups of plants, animals and microorganisms. The green macroalga Ulva flexuosa has a potential to become invasive and this species was investigated for its hitchhiking potential under laboratory conditions. Zoospores of U. flexuosa were maintained at 4°C for nearly 10 months in the dark. Recruitment potential of zoospores after dark stress was tested in a modified Provasoli medium under optimal laboratoryconditions. The success rate of zoospore recruitment was 61%. The paper describes the transfer potential through shipping activities by correlating the Ulva zoospores recruitment potential and survivability.