Restoration of the mycobiome of the endangered Hawaiian mint Phyllostegia kaalaensis increases its resistance to a common powdery mildew

Functions of arbuscular mycorrhizal fungi in regulating endangered species Heptacodium miconioides growth and drought stress tolerance

KEY MESSAGE

The important values of AMF in regulating endangered species Heptacodium miconioides growth and drought stress tolerance. The wild endangered tree Heptacodium miconioides is distributed sporadically in mountainous areas and often subjected to various abiotic stresses, such as drought. The mutualistic association between plants and arbuscular mycorrhizal fungi (AMF) is known to have a significant impact on plant growth and their ability to withstand drought conditions. However, the role of AMF in H. miconioides seedlings in regulating drought tolerance remains unknown. This study investigated the ability of AMF symbionts to mitigate drought and their underlying mechanism on H. miconioides leaves. The results showed that drought stress dramatically decreased the leaf biomass and damaged the chloroplast structure in seedlings. Conversely, inoculation with AMF noticeably alleviated the deleterious effects of drought stress by restoring leaf morphology and improving the photosynthetic capacity. Moreover, plants inoculated with AMF enhanced the proportion of palisade tissue to spongy tissue in the leaves and the size of starch grains and number of plastoglobules in the chloroplast ultrastructure. A transcriptomic analysis showed that 2157 genes (691 upregulated and 1466 downregulated) were differentially expressed between drought stress with AMF inoculation and drought treatment. Further examination demonstrated that the genes exhibiting differential expression were predominantly associated with the advancement of photosynthesis, sucrose and starch metabolism, nitrogen metabolism, chloroplast development, and phenylpropanoid biosynthetic pathways, and the key potential genes were screened. These findings conclusively provided the physiological and molecular mechanisms that underlie improved drought resistance in H. miconioides in the presence of AMF, which could contribute to improving the survival and species conservation of H. miconioides.

Facilitating Reforestation Through the Plant Microbiome: Perspectives from the Phyllosphere

Tree planting and natural regeneration contribute to the ongoing effort to restore Earth's forests. Our review addresses how the plant microbiome can enhance the survival of planted and naturally regenerating seedlings and serve in long-term forest carbon capture and the conservation of biodiversity. We focus on fungal leaf endophytes, ubiquitous defensive symbionts that protect against pathogens. We first show that fungal and oomycetous pathogen richness varies greatly for tree species native to the United States (n = 0-876 known pathogens per US tree species), with nearly half of tree species either without pathogens in these major groups or with unknown pathogens. Endophytes are insurance against the poorly known and changing threat of tree pathogens. Next, we review studies of plant phyllosphere feedback, but knowledge gaps prevent us from evaluating whether adding conspecific leaf litter to planted seedlings promotes defensive symbiosis, analogous to adding soil to promote positive feedback. Finally, we discuss research priorities for integrating the plant microbiome into efforts to expand Earth's forests.

Biogeographic structure of fungal communities in seagrass Halophilia ovalis across the Malay Peninsula

Distributed across both the tropical Atlantic and Pacific oceans, the seagrass Halophilia ovalis stabilizes coastal sediment, thereby preventing shoreline erosion and is also an important food source for megaherbivores such as dugongs. However, seagrass meadows globally are under severe duress due to both climate change and anthropogenic activities. We characterized the mycobiome of Halophilia ovalis at seven sites in the Malay Peninsula using ITS1 rDNA amplicon sequences and investigated differences in fungal community structure. We found that geographic location was a significant factor shaping fungal communities and that marine sediment harboured significantly higher diversity when compared to H. ovalis leaves, roots and rhizomes. Taken together, it is likely that locality rather than specific plant structure determines fungal community structure in H. ovalis. Because the plant mycobiome is known to exert a strong effect on plant health, to maximize the success of future seagrass transplantation and restoration work we propose that these efforts consider the importance of seagrass mycobiomes at all stages.