The ethylene response factor (ERF) transcription factors are integral components of environmental stress signaling cascades, regulating a wide variety of downstream genes related to stress responses and plant development. However, the mechanisms by which ERF genes regulate the heat stress response are not well understood. Here, we uncover the positive role of ethylene signaling, ERF95 and ERF97 in basal thermotolerance of Arabidopsis thaliana. We demonstrate that ethylene signaling-defective mutants exhibit compromised basal thermotolerance, whereas plants with constitutively activated ethylene response show enhanced basal thermotolerance. EIN3 physically binds to the promoters of ERF95 and ERF97. Ectopic constitutive expression of ERF95 or ERF97 increases the basal thermotolerance of plants. In contrast, erf95 erf96 erf97 erf98 quadruple mutants exhibit decreased basal thermotolerance. ERF95 and ERF97 genetically function downstream of EIN3. ERF95 can physically interact with ERF97, and this interaction is heat inducible. ERF95 and ERF97 regulate a common set of target genes, including known heat-responsive genes and directly bind to the promoter of HSFA2. Thus, our study reveals that the EIN3-ERF95/ERF97-HSFA2 transcriptional cascade may play an important role in the heat stress response, thereby establishing a connection between ethylene and its downstream regulation in basal thermotolerance of plants.

The chloroplast and mitochondrion are semi-autonomous organelles that play essential roles in cell function. These two organelles are embellished with prokaryotic remnants and contain many new features emerging from the co-evolution of organelles and the nucleus. A typical plant chloroplast or mitochondrion genome encodes less than 100 genes, and the regulation of these genes' expression is remarkably complex. The regulation of chloroplast and mitochondrion gene expression can be achieved at multiple levels during development and in response to environmental cues, in which, RNA metabolism, including: RNA transcription, processing, translation, and degradation, plays an important role. RNA metabolism in plant chloroplasts and mitochondria combines bacterial-like traits with novel features evolved in the host cell and is regulated by a large number of nucleus-encoded proteins. Among these, pentatricopeptide repeat (PPR) proteins are deeply involved in multiple aspects of the RNA metabolism of organellar genes. Research over the past decades has revealed new insights into different RNA metabolic events in plant organelles, such as the composition of chloroplast and mitochondrion RNA editosomes. We summarize and discuss the most recent knowledge and biotechnological implications of various RNA metabolism processes in plant chloroplasts and mitochondria, with a focus on the nucleus-encoded factors supporting them, to gain a deeper understanding of the function and evolution of these two organelles in plant cells. Furthermore, a better understanding of the role of nucleus-encoded factors in chloroplast and mitochondrion RNA metabolism will motivate future studies on manipulating the plant gene expression machinery with engineered nucleus-encoded factors.

Cold stress is a major environmental factor that adversely affects the growth and productivity of tea plants. Upon cold stress, tea plants accumulate multiple metabolites, including ascorbic acid. However, the role of ascorbic acid in the cold stress response of tea plants is not well understood. Here, we report that exogenous ascorbic acid treatment improves the cold tolerance of tea plants. We show that ascorbic acid treatment reduces lipid peroxidation and increases the Fv/Fm of tea plants under cold stress. Transcriptome analysis indicates that ascorbic acid treatment down-regulates the expression of ascorbic acid biosynthesis genes and ROS-scavenging-related genes, while modulating the expression of cell wall remodeling-related genes. Our findings suggest that ascorbic acid treatment negatively regulates the ROS-scavenging system to maintain ROS homeostasis in the cold stress response of tea plants and that ascorbic acid’s protective role in minimizing the harmful effects of cold stress on tea plants may occur through cell wall remodeling. Ascorbic acid can be used as a potential agent to increase the cold tolerance of tea plants with no pesticide residual concerns in tea.

Purpose: To characterize and correlate guttata severity, Descemet’s membrane thickness (DMT), central cornea thickness (CCT) in corneas with guttae using specular microscopy and spectral-domain optical coherence tomography (SD-OCT) and test the Doheny Image Reading Center (DIRC) specular microscopy-based corneal guttata severity scale. Methods: Forty-nine eyes of 49 patients with guttata and 36 eyes of age-matched of 36 normal controls were enrolled in the study. Three images of the central cornea and four of the peripheral cornea (inferior, superior, nasal and temporal) of each eye were taken using the Konan NSP-9900 specular microscope. A volume scan of the central cornea cross-section was collected on each eye using the Heidelberg Spectralis SD-OCT. The density of endothelial guttata based on specular images was graded on a 0-4 scale and the Descemet’s membrane thickness (DMT) and central corneal thickness (CCT) were manually measured by two trained graders. Results: The DIRC corneal guttata severity scale showed good reproducibility of all corneal endothelial images (weighted Kappa=0.87). Mean DMT was 16.1± 2.4 µm in controls and 25.5 ± 10.9 µm in corneas with guttata (P<0.001). Mean CCT was 552 ± 26 µm in controls and 603 ± 55 µm in corneas with guttata (P<0.001). Guttata severity was significantly correlated with both DMT (r=0.743, P<0.001) and CCT (r=0.569, P<0.001). Age was moderately correlated with DMT (r=0.472, P=0.003) and mildly correlated with guttata severity (r=0.285, P=0.031), but was not correlated with CCT (r=0.058, P=0.681). Guttatta grade 3 corneas displayed increase in DMT and guttata grade 4 was associated with a significant increase in CCT. Conclusions: The DMT and CCT are increased in corneas with guttata. The higher density of guttae is correlated with increased thickness. Specular microscopy combined with SD-OCT can be used as a good approach to assess severity of FECD.

The branching angle of tea plants is a key factor in determining their branching structure, which significantly affects yield, suitability for mechanical harvesting, and overall plant architecture. However, the mechanisms underlying branching angle formation in tea plants remain unclear. In this study, we explored the mechanism of branching angle formation in tea plants by analysing the transcriptome and plant hormone levels of tea plant cultivars with different branching angles. The results indicated that gibberellin positively regulates the branching angle of tea plants, cytokinins, auxin, and abscisic acid involved in the formation of branching angles in tea plants. The transcriptome analysis revealed that candidate regulatory factors, including plant-hormone-related genes (the gibberellin synthesis gene GA3ox1 and metabolism gene GA2ox1; the cytokinin metabolism genes CKX and UGT; the auxin signal transduction-related gene LAX3; and the abscisic acid signal transduction gene PYL4), genes regulating cell division and growth (LAZY1, TAC1, and MAX1), and transcription factors (MYBs, WRKYs, TCPs, AP2/ERFs, and MADS-box), are involved in the formation of branching angles in tea plants. These results offer insights into the mechanism of branching angle formation in tea plants, providing important theoretical reference for the selection and breeding of tea cultivars suitable for mechanical harvesting, thereby improving agricultural efficiency and sustainability.