Diversity characteristics of arbuscular mycorrhizal fungi communities in the soil along successional altitudes of Helan Mountain, arid, and semi-arid regions of China.

Introduction: Arbuscular mycorrhizal fungi (AMF) perform a vital role in terrestrial ecosystems. Methods: To investigate the diversity of AMF communities on the western slope of Helan Mountain at different altitudes and their influence factors, high-throughput sequencing was used to study the structure and diversity of soil AMF communities under different environments and their interrelationships between AMF and environmental factors. Results: The results revealed that there were significant differences (p < 0.05) in the physical and chemical properties of the soil along the different altitudes. A total of 1,145 OTUs were obtained by high-throughput sequencing, belonging to 1 phylum, 4 class, 6 orders, 13 families, 18 genera and 135 species, with the dominant genus being Glomus, which accounted for 75.27% of the relative abundance of the community. Soil AMF community structure was shown to be variable at the generic level according to NMDS analysis. Correlation analysis showed that soil pH, water content (WC), organic matter (OM), available K, available P and N were significantly correlated with AMF community diversity and species abundance (p < 0.05, p < 0.01). Based on redundancy analysis (RDA) and Monte Carlo test results, soil pH, WC and OM had highly significant effects (p < 0.01) on AMF community diversity and species abundance. Discussion: This study investigates the relationship between AMF community structure and diversity and soil physicochemical properties at different elevations on the western slope of Helan Mountain, which is of great significance to the study of the Helan Mountain ecosystem.

Caspase 3-like protease is involved in ethylene-induced programmed cell death during aerenchyma formation in Helianthus annuus stem.

Previous research has reported that hypoxic conditions and ethylene treatments greatly trigger programmed cell death (PCD) occurrence and induce the formation of aerenchyma to adapt stress environment in Helianthus annuus stem. Caspase 3-like protease (CLP) as regulatory signals, also be involved in the process of PCD to adapt the low oxygen environment. However, the relationships between ethylene and CLP have seldom been reported. Herein, To understand the regulatory role of ethylene and CLP signaling molecules in aerenchyma formation, we investigated the effects of exogenous ethephon (ET), ethylene perception inhibitor 1-methylcyclopropene (1-MCP), and the treatment of 1-MCP + ET on morphological, physiological characteristics and aerenchyma formation in H. annuus stem. The results showed that lysigenous aerenchyma formation in H. annuus stem is induced by ET, and immunohistochemistry assay indicate CLP activity is raised at the formation stage of aerenchyma formation, and decreased at the expanding phase of aerenchyma formation. Western blotting illustrate the expression of CLP is also increased within 8 h after ethylene signaling inducing aerenchyma formation, and the activities of CLP are higher in ET treated seedlings than the control and 1-MCP treated seedlings. The same phenomenon was also observed by caspase-3 activity assay. These results revealed there is a causal and interdependent relationship between ET and CLP signaling during the process of aerenchyma formation, which regulating PCD initiation in H. annuus stem.

Programmed cell death associated with the formation of schizo-lysigenous aerenchyma in Nelumbo nucifera root.

Nelumbo nucifera (N. nucifera) is an important aquatic economic crop with high edible, medicinal, ornamental, and ecological restoration values. Aerenchyma formation in N. nucifera root is an adaptive trait to the aquatic environment in long-term evolution. In this study, light microscopy, electron microscopy, and molecular biology techniques were used to study the process of the aerenchyma development and cytological events in N. nucifera root and the dynamic changes of aerenchyma formation under the treatment of exogenous 21% oxygen, ethylene (ET), and ET synthesis i + nhibitor 1-methylcyclopropene (1-MCP). The results showed that programmed cell death (PCD) occurred during the aerenchyma formation in N. nucifera root. Plasmalemma invagination and vacuole membrane rupture appeared in the formation stage, followed by nuclear deformation, chromatin condensation and marginalization, and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) detection was positive at this time. In the expansion stage of the aerenchyma development, cytoplasmic degradation and many vesicles appeared in the cytoplasm, and organelles began to degrade. Then the plasma membrane began to degrade, and the degradation of the cell wall was the last PCD step. After 21% oxygen was continuously filled in the rhizosphere environment of N. nucifera roots, the area of aerenchyma in N. nucifera roots was smaller than that in the control group. Moreover, ET induced the earlier occurrence of aerenchyma in N. nucifera root, but also, the area of aerenchyma became larger than that of the control. On the contrary, 1-MCP inhibited the occurrence of aerenchyma to some extent. Therefore, the formation of aerenchyma in N. nucifera root resulted from PCD, and its formation mode was schizo-lysigenous. A hypoxic environment could induce aerenchyma formation in plants. ET signal was involved in aerenchyma formation in N. nucifera root and had a positive regulatory effect. This study provides relevant data on the formation mechanism of plant aerenchyma and the cytological basis for exploring the regulation mechanism of plant aerenchyma formation.