Canker disease caused by Neoscytalidium dimidiatum is the most serious disease that attacks the pitaya industry. One pathogenic fungus, referred to as ND8, was isolated from the wild-type red-fleshed pitaya (Hylocereus polyrhizus) of Hainan Province. In the early stages of this disease, stems show little spots and a loss of green color. These spots then gradually spread until the stems became rotten due to infection by various strains. Canker disease caused by Neoscytalidium dimidiatum poses a significant threat to pitaya commercial plantations with the growth of stems and the yields, quality of pitaya fruits. However, a lack of transcriptomic and genomic information hinders our understanding of the molecular mechanisms underlying the pitaya defense response. We investigated the host responses of red-fleshed pitaya (H. polyrhizus) cultivars against N. dimidiatum using Illumina RNA-Seq technology. Significant expression profiles of 23 defense-related genes were further analyzed by qRT-PCR. The total read length based on RNA-Seq was 25,010,007; mean length was 744, the N50 was 1206, and the guanine-cytosine content was 44.48%. Our investigation evaluated 33,584 unigenes, of which 6209 (18.49%) and 27,375 (81.51%) were contigs and singlets, respectively. These unigenes shared a similarity of 16.62% with Vitis vinifera, 7.48% with Theobroma cacao, 6.6% with Nelumbo nucifera and 5.35% with Jatropha curcas. The assembled unigenes were annotated into non-redundant (NR, 25161 unigenes), Kyoto Encyclopedia of Genes and Genomes (KEGG, 17895 unigenes), Clusters of Orthologous Groups (COG, 10475 unigenes), InterPro (19,045 unigenes), and Swiss-Prot public protein databases (16,458 unigenes). In addition, 24 differentially expressed genes, which were mainly associated with plant pathology pathways, were analyzed in-depth. This study provides a basis for further in-depth research on the protein function of the annotated unigene assembly with cDNA sequences.

Potassium (K⁺) is an abundant and important macronutrient for plants. It plays crucial roles in many growth and developmental processes, and growth is inhibited under low −K⁺ conditions. The molecular mechanisms operating under K⁺ starvation have been little reported in banana, which is a non-model plant. We conducted a transcriptome analysis of banana (Musa acuminata L. AAA group, cv. Cavendish) in response to low −K⁺ stress. The phenotypic traits and transcriptomic profiles of banana leaves and roots were compared between low −K⁺ (LK) and normal −K⁺ (NK) groups. The phenotypic parameters for the LK group, including fresh and dry weight, were lower than those for the NK group, which suggested that low −K⁺ stress may inhibit some important metabolic and biosynthetic processes. K⁺ content and biomass were both decreased in the LK group compared to the NK group. Following ribonucleic acid sequencing (RNA-Seq), a total of 26,796 expressed genes were detected in normal −K⁺ leaves (NKL), 27,014 were detected in low −K⁺ leaves (LKL), 29,158 were detected in normal −K⁺ roots (NKR), and 28,748 were detected in low −K⁺ roots (LKR). There were 797 up-regulated differentially expressed genes (DEGs) and 386 down-regulated DEGs in NKL versus LKL, while there were 1917 up-regulated DEGs and 2830 down-regulated DEGs in NKR versus LKR. This suggested that the roots were more sensitive to low −K⁺ stress than the leaves. DEGs related to K⁺ transport and uptake were analyzed in detail. Gene functional classification showed that the expression of genes regarding ABC transporters, protein kinases, transcription factors, and ion transporters were also detected, and may play important roles during K⁺ deficiency.

Bananas are an important part of the diets of millions of people around the globe. Low P absorption and use efficiency significantly restrict banana yields. To further explore the molecular mechanisms of P regulation in banana plants, we used RNA sequencing-based transcriptomic analysis for banana plants subjected to Pi deficit stress for 60 days. We detected 1900 significantly differentially expressed genes (DEGs) in aboveground plant parts and 7398 DEGs in root parts under low P stress. Gene ontology (GO) classification analysis showed that 156,291 GO terms belonging to molecular functions, 53,114 GO terms belonging to cellular components, and 228,544 GO terms belonging to biological processes were enriched in the aboveground and root components. A number of DEGs involved in energy metabolism-related processes, signal transduction, control of rhizosphere P activation, and Pi mobilization were found, which were confirmed by quantitative reverse-transcription Polymerase Chain Reaction (qRT-PCR) analysis. At the transcriptomic level, we detected 13 DEGs from different organs and with different functions in the time-course response to phosphorus deficiency stress. These DEGs may include some key genes that regulate the phosphorus network, increasing our understanding of the molecular mechanism of Pi homeostasis in banana. These findings will also help develop biotechnologies to create a variant of banana with more effective Pi absorption and utilization.

Coral reefs are increasingly threatened by global climate change, and mass bleaching and mortality events caused by elevated seawater temperature have led to coral loss worldwide. Hainan Island hosts extensive coral reef ecosystems in China, yet seasonal variation in Symbiodiniaceae communities within this region remains insufficiently understood. We aimed to investigate the temperature-driven adaptability regulation of the symbiotic Symbiodiniaceae community in reef-building corals, focusing on the environmental adaptive changes in its community structure in coral reefs between cold (23.6–24.6 °C) and warm (28.2–30.6 °C) months. Symbiodiniaceae shuffling and rare genotype turnover were discovered in adaptability variations in the symbiotic Symbiodiniaceae community between two months. Symbiodiniaceae genetic diversity increased during warm months, primarily due to temporal turnover of rare genotypes within the Cladocopium and Durusdinium genera. Coral Favites, Galaxea, and Porites exhibited the shuffling of Symbiodiniaceae between tolerant Durusdinium and sensitive Cladocopium. Symbiodiniaceae interactions in G. fascicularis and P. lutea exhibited the highest levels of stability with the increase in temperature, whereas the interactions in A. digitifera and P. damicornis showed the lowest levels of stability. Rare genotypes functioned as central hubs and important roles within Symbiodiniaceae communities, exhibiting minimal responsiveness to temperature fluctuations while maintaining community structural stability. The temperature-driven adaptability regulation of symbiotic Symbiodiniaceae could be achieved by Symbiodiniaceae shuffling and rare genotype turnover. The process might be aggravated by concurrent adverse factors, including elevated salinity, pollution, and anthropogenic disturbance. These findings provide insights into how the Symbiodiniaceae community influences the adaptation and resilience of coral hosts to temperature fluctuations in coral reefs. Furthermore, they may contribute to assessing the reef-building coral’s capacity to withstand environmental stressors associated with global climate change.

Ocean acidification (OA), driven by global climate change together with pollution from organic contaminants, is increasing the ecological risk faced by coral reef ecosystems. The coral holobiont comprises diverse microbial communities that collectively support the coral host in coping with and adapting to environmental stress. However, the response of the coral holobiont to the combined stress of acidification and benzo[a]pyrene (BaP) remains poorly understood. In this study, Acropora millepora was selected as a model species to investigate the responses of coral-associated microbiomes to acidification (pH 7.8), BaP exposure (10 µg·L⁻¹) and their combined effects. We found that while the cell density of coral-associated Symbiodiniaceae increased significantly with prolonged exposure time in all treatment groups, and there were no temporal differences in chlorophyll-a contents. The Symbiodiniaceae community was stable within all treatments, with Cladocopium as the dominant genus, and subtype C3u had the highest relative abundance (>70%). A rapid and significant increase in rare bacteria taxa was observed in the single-stress treatments (acidification, BaP), whereas prolonged exposure led to an increasing number of unique bacteria taxa in the combined-stress group in two weeks. Surprisingly, the main community structure of core coral-associated bacteria in the combined treatment group was close to that of the control group. Across all treatments, core coral-associated bacteria (including Sphingomonadaceae and Burkholderiaceae) consistently dominated the microbial community, while core coral-associated archaea exhibited more stochastic variations. Collectively, these results highlight the critical role of coral-associated microbiomes in rapidly and flexibly responding to environmental stressors, thereby contributing to the maintenance of holobiont stability under multiple stress conditions.