Epigenetic modifications of 45S rDNA associates with the disruption of nucleolar organisation during Cd stress response in Pakchoi.

The role of the nucleolus in Pakchoi response to Cd stress remains largely unknown. In this work, we focus on exploring the underling mechanism between nucleolus disruption and epigenetic modification in Cd stressed-Pakchoi. Our results indicated that the proportion of nucleolus disruption, decondensation of 45 S rDNA chromatin, and a simultaneous increase in 5' external transcribed spacer region (ETS) transcription were observed with increasing Cd concentration, accompanied by genome-wide alterations in the levels of histone acetylation and methylation. Further results showed that Cd treatment exhibited a significant increase in H3K9ac, H4K5ac, and H3K9me2 levels occurred in promoter regions of the 45 S rDNA. Additionally, DNA methylation assays in the 45 S rDNA promoter region revealed that individual site-specific hypomethylation may be engaged in the activation of 45 S rDNA transcription. Our study provides some molecular mechanisms for the linkage between Cd stress, rDNA epigenetic modifications, and nucleolus disintegration in plants.

IbMYC2 Contributes to Salt and Drought Stress Tolerance via Modulating Anthocyanin Accumulation and ROS-Scavenging System in Sweet Potato.

Basic helix-loop-helix (bHLH) transcription factors extensively affect various physiological processes in plant metabolism, growth, and abiotic stress. However, the regulation mechanism of bHLH transcription factors in balancing anthocyanin biosynthesis and abiotic stress in sweet potato (Ipomoea batata (L.) Lam.) remains unclear. Previously, transcriptome analysis revealed the genes that were differentially expressed among the purple-fleshed sweet potato cultivar 'Jingshu 6' and its anthocyanin-rich mutant 'JS6-5'. Here, we selected one of these potential genes, IbMYC2, which belongs to the bHLH transcription factor family, for subsequent analyses. The expression of IbMYC2 in the JS6-5 storage roots is almost four-fold higher than Jingshu 6 and significantly induced by hydrogen peroxide (H2O2), methyl jasmonate (MeJA), NaCl, and polyethylene glycol (PEG)6000. Overexpression of IbMYC2 significantly enhances anthocyanin production and exhibits a certain antioxidant capacity, thereby improving salt and drought tolerance. In contrast, reducing IbMYC2 expression increases its susceptibility. Our data showed that IbMYC2 could elevate the expression of anthocyanin synthesis pathway genes by binding to IbCHI and IbDFR promoters. Additionally, overexpressing IbMYC2 activates genes encoding reactive oxygen species (ROS)-scavenging and proline synthesis enzymes under salt and drought conditions. Taken together, these results demonstrate that the IbMYC2 gene exercises a significant impact on crop quality and stress resistance.

Equilibrium price estimation of green bonds from the perspective of resource allocation.

Green bonds offer substantial positive externalities compared to other types of bonds. This leads to a resource distribution efficiency that falls below the optimal level dictated by Pareto efficiency. It becomes essential to determine a means by which green bonds can achieve an equilibrium price, ensuring optimal public resource allocation and maximized social welfare. From the perspective of externalities, this study employs the carbon shadow price (CSP) to determine the equilibrium price of carbon emissions. Subsequently, this value aids in estimating the equilibrium price of green bonds. Firstly, we introduced an optimized bootstrap method to estimate the bias-corrected CSP at the provincial level in China from 2007 to 2020. Then, a pricing framework is developed, integrating both the carbon trading price and the estimated CSP, to determine the green bond's equilibrium price. Numerical simulations indicate that, under current conditions, green bonds cannot achieve the equilibrium price by relying solely on the carbon trading mechanism. Therefore, further development of China's carbon emissions trading market is required.

Expression of the Sweet Potato MYB Transcription Factor IbMYB48 Confers Salt and Drought Tolerance in Arabidopsis.

Sweet potato (Ipomoea batatas (L.) Lam) is one of the most crucial food crops widely cultivated worldwide. In plants, MYB transcription factors play crucial roles in plant growth, defense regulation, and stress resistance. However, the regulatory mechanism of MYBs in salt and drought response remain poorly studied in sweet potato. By screening a transcriptome database for differentially expressed genes between the sweet potato variety Jingshu 6 and its mutant JS6-5 with high anthocyanin and increased tolerance to salt and drought stresses, we identified a R2R3-MYB gene IbMYB48, for which expression was induced by PEG6000, NaCl, abscisic acid (ABA), methyl jasmonic acid (MeJA), salicylic acid (SA) and H2O2. Particle-mediated transient transformation of onion epidermal cells showed IbMYB48 is localized in the nucleus. Transactivation activity assay in yeast cells revealed that IbMYB48 has transactivation activity, and its active domain is located in the carboxyl (C)-terminal region. Furthermore, expression of IbMYB48 confers enhanced tolerance to salt and drought stresses in transgenic Arabidopsis. The contents of endogenous ABA, JA, and proline in transgenic lines were higher than control, and the activity of superoxide dismutase (SOD) was significantly increased under salt and drought stress conditions. By contrast, the accumulation of malondialdehyde (MDA) and H2O2 were lower. Moreover, genes encoding enzymes involved in ABA biosynthetic pathway, JA biosynthesis and signaling pathway, and reactive oxygen species (ROS) scavenging system were significantly up-regulated in transgenic Arabidopsis under salt or drought stress. Altogether, these results suggest IbMYB48 may be a candidate gene for improvement of abiotic stress tolerance.

A novel sweetpotato RING-H2 type E3 ubiquitin ligase gene IbATL38 enhances salt tolerance in transgenic Arabidopsis.

Arabidopsis Toxicos en Levadura (ATL) proteins compose a subfamily of E3 ubiquitin ligases and play major roles in regulating plant growth, cold, drought, oxidative stresses response and pathogen defense in plants. However, the role in enhancing salt tolerance has not been reported to date. Here, we cloned a novel RING-H2 type E3 ubiquitin ligase gene, named IbATL38, from sweetpotato cultivar Lushu 3. This gene was highly expressed in the leaves of sweetpotato and strongly induced by NaCl and abscisic acid (ABA). This IbATL38 was localized to nucleus and plasm membrane and possessed E3 ubiquitin ligase activity. Overexpression of IbATL38 in Arabidopsis significantly enhanced salt tolerance, along with inducible expression of a series of stress-responsive genes and prominently decrease of H2O2 content. These results suggest that IbATL38 as a novel E3 ubiquitin ligase may play an important role in salt stress response.

Abundance and morphology of charcoal in sediments provide no evidence of massive slash-and-burn agriculture during the Neolithic Kuahuqiao culture, China.

It remains debatable whether slash-and-burn practices were adopted in rice cultivation by the Neolithic Kuahuqiao culture in the Ningshao Plain, one of the birthplaces of rice farming. Here, we established charcoal-based indices to reconstruct the history of fire and vegetation in the Ningshao Plain since the last glacial period. We collected representative modern vegetation and conducted combustion and fragmentation experiments to simulate fire and depositional processes, respectively. Charcoals from modern vegetation show clear morphological differences between herbaceous and woody plants. In particular, the length to width ratios (L/W) of herbaceous charcoals were systematically higher than those of woody charcoals, and the associated end-member values were 4.50 and 1.94, respectively. These values were then applied to sediment cores (KHQ-14/15) collected in proximity to the Kuahuqiao archaeological site. Results show that the amount of combusted herbaceous plants increased sharply after the Holocene, and the most remarkable rise occurred around 8550 yr B.P. This observation may reflect local environment (sedimentary and/or climatic) changes or small-scale early human activities. During the Kuahuqiao cultural period (8250-7450 yr B.P.), the relative abundance of woody charcoals increased, but the overall fire intensity decreased. This finding suggests that the Kuahuqiao farming was restricted to a small geographic area and large-scale slash-and-burn farming activities were not adopted.