Physiological analysis and transcriptome sequencing reveal the effects of drier air humidity stress on Pterocarya stenoptera

Multi-omics analyses provide insights into the evolutionary history and the synthesis of medicinal components of the Chinese wingnut

Chinese wingnut (Pterocarya stenoptera) is a medicinally and economically important tree species within the family Juglandaceae. However, the lack of high-quality reference genome has hindered its in-depth research. In this study, we successfully assembled its chromosome-level genome and performed multi-omics analyses to address its evolutionary history and synthesis of medicinal components. A thorough examination of genomes has uncovered a significant expansion in the Lateral Organ Boundaries Domain gene family among the winged group in Juglandaceae. This notable increase may be attributed to their frequent exposure to flood-prone environments. After further differentiation between Chinese wingnut and Cyclocarya paliurus, significant positive selection occurred on the genes of NADH dehydrogenase related to mitochondrial aerobic respiration in Chinese wingnut, enhancing its ability to cope with waterlogging stress. Comparative genomic analysis revealed Chinese wingnut evolved more unique genes related to arginine synthesis, potentially endowing it with a higher capacity to purify nutrient-rich water bodies. Expansion of terpene synthase families enables the production of increased quantities of terpenoid volatiles, potentially serving as an evolved defense mechanism against herbivorous insects. Through combined transcriptomic and metabolomic analysis, we identified the candidate genes involved in the synthesis of terpenoid volatiles. Our study offers essential genetic resources for Chinese wingnut, unveiling its evolutionary history and identifying key genes linked to the production of terpenoid volatiles.

Molecular mechanism of thiamine in mitigating drought stress in Chinese wingnut (Pterocarya stenoptera): Insights from transcriptomics

Urban garden plants are frequently affected by drought, which can hinder their growth, development, and greening effect. Previous studies have indicated that Chinese wingnut (Pterocarya stenoptera) responds to drought stress by increasing the expression of thiamine synthesis genes. In this study, it was found that exogenous thiamine can effectively alleviate the negative effects of drought stress on plants. Forward transcriptome sequencing and physiological tests were further conducted to reveal the molecular mechanism of thiamine in alleviating drought stress. Results showed that exogenous thiamine activated the expression of eight chlorophyll synthesis genes in Chinese wingnut under drought stress. Moreover, physiological indicators proved that chlorophyll content increased in leaves of Chinese wingnut with thiamine treatment under drought stress. Photosynthesis genes were also activated in Chinese wingnut treated with exogenous thiamine under drought stress, as supported by photosynthetic indicators PIabs and PItotal. Additionally, exogenous thiamine stimulated the expression of genes in the auxin-activated signaling pathway, thus attenuating the effects of drought stress. This study demonstrates the molecular mechanism of thiamine in mitigating the effects of drought stress on non-model woody plants lacking transgenic systems. This study also provides an effective method to mitigate the negative impacts of drought stress on plants.

High-resolution imaging of O2 dynamics and metal solubilization in the rhizosphere of the hyperaccumulator Leersia hexandra Swartz

The mobilization of trace metals in the rhizosphere can be affected by the redox potential, which is closely related to the O₂ dynamics. This study examined the distributions of O₂ and trace metals in the rhizosphere of the subaquatic hyperaccumulator Leersia hexandra Swartz under chromium (Cr) stress using planar optodes and the diffusive gradients in thin films technique coupled with laser ablation inductively coupled plasma mass spectrometry. The O₂ concentrations and oxidized areas in the rhizosphere significantly increased with increases in the light intensity, air humidity, and atmospheric CO₂ concentrations (p < 0.05). The O₂ concentration first increased with increasing ambient temperatures, then decreased when the temperature increased from 25 to 32 ℃. The O₂ concentration in the rhizosphere was significantly decreased under Cr stress (p < 0.05), with a prolonged response time to the altered ambient temperature. Cr stress led to decreased mobilities of As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Sb, V, W, and Zn in the rhizosphere, which were negatively correlated with the concentrations of O₂. These results provide new insights into the role of changes in the O₂ concentration induced by the roots of hyperaccumulator plants in controlling the mobility of trace metals in soils.

Transcriptomic responses and physiological changes to cold stress among natural populations provide insights into local adaptation of weeping forsythia

Genetic mechanisms of species local adaptation are an emerging topic of great interest in evolutionary biology and molecular ecology. In this study, we compared the changes of physiological and phenotypic indexes and gene expression of four weeping forsythia populations under cold stress through a common garden experiment. Physiological and phenotypic results showed that there were differences in cold tolerance among populations. cold tolerance of high the latitude population (HBWZ) was the strongest, followed by the middle latitude population (SXWL), while the low latitude populations (SXHM) and (SXLJ) expressed the weakest cold tolerance. We identified significant differences in gene expression of cold tolerance related pathways and ontologies, including genes of oxylipin and isoquinoline alkaloid biosynthetic process, galactose, tyrosine and unsaturated fatty acids metabolism, among these populations under the same experimental temperature treatments. Even under the same degree of stress, there were notable differences in gene expression among natural populations. In this study, we present a working model of weeping forsythia populations which evolved in the context of different intensities of cold stress. Our study provides new insights for comprehending the genetic mechanisms of local adaptation for non-model species.

Transcriptomic responses to drought stress among natural populations provide insights into local adaptation of weeping forsythia

BACKGROUND

Understanding the genetic mechanisms of local adaptation is an important emerging topic in molecular ecology and evolutionary biology.

RESULTS

Here, we identify the physiological changes and differential expression of genes among different weeping forsythia populations under drought stress in common garden experiments. Physiological results showed that HBWZ might have higher drought tolerance among four populations. RNA-seq results showed that significant differential expression in the genes responding to the synthesis of flavonoids, aromatic substances, aromatic amino acids, oxidation-reduction process, and transmembrane transport occured among four populations. By further reanalysis of results of previous studies, sequence differentiation was found in the genes related to the synthesis of aromatic substances among different weeping forsythia populations.

CONCLUSIONS

Overall, our study supports the hypothesis that the dual differentiation in gene efficiency and expression increases among populations in response to heterogeneous environments and is an important evolutionary process of local adaptation. Here, we proposed a new working model of local adaptation of weeping forsythia populations under different intensities of drought stress, which provides new insights for understanding the genetic mechanisms of local adaptation for non-model species.