Exogenous application of melatonin to mitigate drought stress-induced oxidative damage in Phoebe sheareri seedlings.

Background: Drought stress is a major prevalent environmental factor impairing growth. Melatonin mitigates the impacts of drought stress on plants. However, melatonin's role in Phoebe sheareri (Hemsl.) Gamble (P. sheareri) is unknown. We aimed to reveal the protective effects of melatonin on P. sheareri seedlings under drought conditions. Methods: Melatonin was sprayed under drought or normal water conditions. The parameters, including growth, physiological factors, and phytohormones of P. sheareri, were examined. Results: Compared to the normal control group, drought stress inhibited the growth of seedlings and significantly reduced the content of carotenoids, SOD, POD, APX, PPO, CAT, GR, and soluble sugars, and increased the contents of MDA, O2 •-, proline, soluble proteins, ABA, and JA-Me in P. sheareri seedlings. However, melatonin treatment significantly reversed the adverse drought-induced responses and promoted the P. sheareri seedling's growth. Moreover, the heatmap and principal component analysis suggested a high similarity in the behavior patterns of the six measured antioxidant enzymes in P. sheareri seedlings. Conclusion: Our study reported for the first time that melatonin has a protective role in P. sheareri seedlings under drought-stress conditions. This role is related to ROS scavenging, activation of antioxidant enzymes, and crosstalk of phytohormones. This study provided a theoretical basis for improving the ability of P. sheareri adapted to arid environments.

The Role of PnTCP2 in the Lobed Leaf Formation of Phoebe neurantha var. lobophylla.

A lobed leaf is a common trait in plants, but it is very rare in Lauraceae plants, including species of Phoebe. In the study of germplasm resources of Phoebe neurantha, we found lobed leaf variant seedlings, and the variation could be inherited stably. Studying the lobed leaf mechanism of P. neurantha var. lobophylla can offer insight into the leaf development mechanism of woody plants. RNA-seq and small RNA-seq analysis results showed that a total of 8091 differentially expressed genes (DEGs) and 16 differentially expressed miRNAs were identified in P. neurantha var. lobophylla. Considering previous research results, a leaf margin morphological development related miRNA, pne-miRNA319a, was primary identified as a candidate miRNA. Target gene prediction showed that a total of 2070 genes were predicted to be the target genes of differentially expressed miRNAs. GO enrichment analysis of differentially expressed target genes suggested that PnTCP2 is related to lobed leaf formation. The TRV-VIGS gene silencing of PnTCP2 led to lobed leaves in P. neurantha seedlings. The downregulation of PnTCP2 led to lobed leaves. The yeast two-hybrid test and bimolecular fluorescence complementation test confirmed that the PnTCP2 protein interacted with the PnLBD41 protein. Based on the expression analysis of gene-silenced leaves and RNA-seq and small RNA-seq analysis results, pne- miRNA319a and PnLBD41 might also play important roles in this process. In conclusion, PnTCP2 plays an important and vital role in the formation of the lobed leaves of P. neurantha var. lobophylla.

Comparative Transcriptome Analysis Revealing the Potential Mechanism of Low-Temperature Stress in Machilus microcarpa.

Machilus microcarpa is a rare national tree species in China and possesses important ornamental and ecological value. M. microcarpa can be planted in low-temperature areas, depending on whether its seedlings can withstand the harm. To face this problem, the annual seedlings of M. microcarpa were subjected to five temperature treatments, and eight physiological indicators were measured. Furthermore, comparative transcriptome analysis was performed between M. microcarpa leaves treated at 25°C and -2.8°C. A total of 9,385 differentially expressed genes (DEGs) were involved in low-temperature stress in M. microcarpa. An upregulated (cobA) and five downregulated (HEM, CHLM, CRD, CLH, and PORA) genes associated with the porphyrin and chlorophyll metabolism pathway may reduce chlorophyll synthesis under low-temperature stress. Upregulation of six DEGs (two GAPDHs, PFK, PGAM, PDC, and PK) involved in the glycolysis/gluconeogenesis pathway provided energy for M. microcarpa under adverse cold conditions. Thirteen upregulated and seven downregulated genes related to antioxidant enzymes were also observed under low-temperature stress. Candidate transcription factors (TFs) played key roles in signal transduction under low-temperature stress in M. microcarpa, and quantitative real-time PCR (qRT-PCR) analysis validated the RNA-seq data. The results provide valuable information for further studies on the cold response mechanisms for low-temperature stress in M. microcarpa.

Characteristics of Picea neoveitchii tree growth in mountain areas of central China: insights from isotopic compositions and satellite-derived indices.

Leaf nitrogen (N) status and stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) were used to study environmental factors that control mountain individuals of Picea neoveitchii trees, a coniferous species endemic and endangered in China. From May to September 2016, we carried out observations at four different altitude locations extending southeast of Daba Mountain in western Hubei Province. Needle-shaped leaf δ13C was positively correlated with needle N and C content calculated from the needle area (Narea and Carea content), needle δ15N, needle mass, and leaf mass per area (LMA), respectively. Needle δ15N was also positively correlated with monthly temperature and precipitation for the current month and last month. The seasonal normalised difference vegetation index (NDVI) was highest in June at the lowest altitude and August at the highest altitude. We found that N availability as an important driving factor for tree growth is controlled by surface soil temperature, while in summer, air temperatures above 23 °C exceed the physiological threshold of trees and limit the growth of trees. We concluded that the negative effect of higher temperature on tree growth is greater than the positive effect of higher nitrogen.

Differential Expression of MicroRNAs During Root Formation in Taxus Chinensis Var. mairei Cultivars.

MicroRNAs (miRNAs) have been shown to play key roles in the regulation of plant growth and development by modifying the expression of their target genes. However, the influence of miRNAs on root formation and development in woody plants, such as Taxus chinensis, remains largely unknown. In the current study, we explored the phytohormone-response and nutrition-response miRNA expression profiles during T. chinensis rooting by quantitative real-time PCR (qPCR). We identified six phytohormone-response miRNAs, namely, miR164a, miR165, miR167a, miR171b, miR319, and miR391, and eight nutrition-response miRNAs, namely, miR169b, miR395a, miR399c, miR408, miR826, miR827, miR857, and miR2111a, that were differentially expressed at different rooting phases of T. chinensis. Using northern blot analysis of the putative target genes of these miRNAs, we detected the relative gene expression changes of the target genes. Taken together, our results suggest that miRNAs are involved in root formation of T. chinensis and that miRNAs may play important regulatory roles in primary root, crown root, and root hair formation by targeting phytohormone and/or nutrition response genes in T. chinensis. For the first time, these results expand our understanding of the molecular mechanisms of plant root formation and development in a conifer species.

Biological significance of RNA editing in cells.

RNA editing is one of the post-transcriptional RNA processes. RNA editing generates RNA and protein diversity in eukaryotes and results in specific amino acid substitutions, deletions, and changes in gene expression levels. Adenosine-to-inosine RNA editing represents the most important class of editing in human and affects function of many genes. The importance of balancing RNA modification levels across time and space is becoming increasingly evident. In this review, we overview the biological significance of RNA editing including RNA editing in tumorigenesis, RNA editing in neuronal tissues, RNA editing as a regulator of gene expression, and RNA editing in dsRNA-mediated gene silencing, which may increase our understanding of RNA biology.