Condensed tannin accretions specifically distributed in mesophyll cells of non-salt secretor mangroves help in salt tolerance.

MAIN CONCLUSION: Auto-fluorescent condensed tannins specifically accumulated in mesophyll cells of non-salt secretor mangroves are involved in the compartmentation of Na+ and osmotic regulation, contributing to their salt tolerance. Salinity is a major abiotic stress affecting the distribution and growth of mangrove plants. The salt exclusion mechanism from salt secretor mangrove leaves is quite known; however, salt management strategies in non-salt secretor leaves remain unclear. In this study, we reported the auto-fluorescent inclusions (AFIs) specifically accumulated in mesophyll cells (MCs) of four non-salt secretor mangroves but absent in three salt secretors. The AFIs increased with the leaf development under natural condition, and applied NaCl concentrations applied in the lab. The AFIs in MCs were isolated and identified as condensed tannin accretions (CTAs) using the dye dimethyl-amino-cinnamaldehyde (DMACA), specific for condensed tannin (CT), both in situ leaf cross sections and in the purified AFIs. Fluorescence microscopy and transmission electron microscope (TEM) analysis indicated that the CTAs originated from the inflated chloroplasts. The CTAs had an obvious membrane and could induce changes in shape and fluorescence intensity in hypotonic and hypertonic NaCl solutions, suggesting CTAs might have osmotic regulation ability and play an important role in the osmotic regulation in MCs. The purified CTAs were labeled by the fluorescent sodium-binding benzofuran isophthalate acetoxymethyl ester (SBFI-AM), confirming they were involved in the compartmentation of excess Na+ in MCs. This study provided a new view on the salt resistance-associated strategies in mangroves.

Combined metabolome and transcriptome analysis reveals a critical role of lignin biosynthesis and lignification in stem-like pneumatophore development of the mangrove Avicennia marina.

MAIN CONCLUSION: Transcriptional and metabolic regulation of lignin biosynthesis and lignification plays crucial roles in Avicennia marina pneumatophore development, facilitating its adaptation to coastal habitats. Avicennia marina is a pioneer mangrove species in coastal wetland. To cope with the periodic intertidal flooding and hypoxia environment, this species has developed a complex and extensive root system, with its most unique feature being a pneumatophore with a distinct above- and below-ground morphology and vascular structure. However, the characteristics of pneumatophore lignification remain unknown. Studies comparing the anatomy among above-ground pneumatophore, below-ground pneumatophore, and feeding root have suggested that vascular structure development in the pneumatophore is more like the development of a stem than of a root. Metabolome and transcriptome analysis illustrated that the accumulation of syringyl (S) and guaiacyl (G) units in the pneumatophore plays a critical role in lignification of the stem-like structure. Fourteen differentially accumulated metabolites (DAMs) and 10 differentially expressed genes involved in the lignin biosynthesis pathway were targeted. To identify genes significantly associated with lignification, we analyzed the correlation between 14 genes and 8 metabolites and further built a co-expression network between 10 transcription factors (TFs), including 5 for each of MYB and NAC, and 23 enzyme-coding genes involved in lignin biosynthesis. 4-Coumarate-CoA ligase, shikimate/quinate hydroxycinnamoyl transferase, cinnamyl alcohol dehydrogenase, caffeic acid 3-O-methyltransferase, phenylalanine ammonia-lyase, and peroxidase were identified to be strongly correlated with these TFs. Finally, we examined 9 key candidate genes through quantitative real-time PCR to validate the reliability of transcriptome data. Together, our metabolome and transcriptome findings reveal that lignin biosynthesis and lignification regulate pneumatophore development in the mangrove species A. marina and facilitate its adaptation to coastal habitats.

The associations among gratitude, job crafting, teacher-student relationships, and teacher psychological well-being.

Introduction: This study explores the complex dynamics among gratitude, job crafting, teacher psychological well-being, and teacher-student relationships within the context of Chinese English as a Foreign Language (EFL) teachers. Methods: A sample of 456 Chinese EFL teachers participated in this study. Valid scales were administered to collect data on gratitude, job crafting, teacher psychological well-being, and teacher-student relationships. Structural Equation Modeling (SEM) was employed to investigate these relationships. Results: The findings reveal significant connections between gratitude, job crafting, teacher psychological well-being, and teacher-student relationships. SEM analysis demonstrates that gratitude and job crafting have direct effects on teacher psychological well-being. Furthermore, teacher-student relationships were identified as a mediator in these relationships. Discussion: This study underscores the importance of gratitude and job crafting in enhancing the psychological well-being of EFL teachers. It highlights the mediating role of positive teacher-student relationships in the associations between gratitude, job crafting, and teacher psychological well-being. These results have implications for the development of interventions and practices aimed at promoting gratitude, job crafting, and positive teacher-student relationships in the EFL teaching context.

Calcium regulates the physiological and molecular responses of Morus alba roots to cadmium stress.

Heavy metal cadmium (Cd) is toxic to organisms. Mulberry (Morus alba L.) is a fast-growing perennial that is also an economical Cd phytoremediation material with large biomass. However, the molecular mechanisms underlying its Cd tolerance remain unclear. Here, we reveal the physiological and molecular mechanisms underlying Cd toxicity under varying calcium (Ca) treatments. First, under low-Ca treatment (0.1 mM Ca), mulberry growth was severely inhibited and the root surface structure was damaged by Cd stress. Second, electrophysiological data demonstrated that 0.1 mM Ca induced an increased Cd2+ influx, leading to its accumulation in the entire root and root cell walls. Third, high-Ca treatment (10 mM Ca) largely alleviated growth inhibition, activated antioxidant enzymes, increased Ca content, decreased Cd2+ flux, and inhibited Cd uptake by roots. Finally, 0.1 mM Ca resulted in the activation of metal transporters and the disruption of Ca signaling-related gene expression, which facilitated Cd accumulation in the roots, aggravating oxidative stress. These adverse effects were reversed by treatment with 10 mM Ca. This study preliminarily revealed the mechanism by which varying Ca levels regulate Cd uptake and accumulation in mulberry roots, provided an insight into the interrelationships between Ca and Cd in the ecological and economic tree mulberry and offered a theoretical basis for Ca application in managing Cd pollution.