Identification and Functional Prediction of CircRNAs in Leaves of F1 Hybrid Poplars with Different Growth Potential and Their Parents.

Circular RNAs (CircRNAs) regulate plant growth and development; however, their role in poplar heterosis is unclear. We identified 3722 circRNAs in poplar leaves, most of which were intergenic (57.2%) and exonic (40.2%). The expression of circRNAs in F1 hybrids with high growth potential was higher than that in those with low growth potential. Non-additive expression of circRNAs and single-parent expression of circRNAs (SPE-circRNAs) might regulate poplar heterosis through microRNA sponging and protein translation, respectively. DECs among F1 hybrids with different growth potentials might regulate the growth potential of poplar via microRNA sponging. Correlation analysis between circRNA expression and its parent gene expression showed that SPE-M circRNA (circRNAs expressed by male parent only) might regulate poplar heterosis by inhibiting parent gene expression, while other circRNAs might regulate poplar heterosis by enhancing parent gene expression. Weighted correlation network analysis of gene/circRNA expression showed that circRNAs mainly regulate poplar heterosis via carbohydrate metabolism, amino acid metabolism, energy metabolism, and material transport. In addition, we identified seven circRNAs that positively or negatively regulate poplar heterosis. Thus, non-additively expressed circRNAs and SPE circRNAs are involved in regulating poplar heterosis, and DECs among F1 hybrids with different growth potentials were involved in regulating poplar growth potential.

Differences in phyllosphere microbiomes among different Populus spp. in the same habitat.

Introduction: The above-ground parts of terrestrial plants are collectively known as the phyllosphere. The surface of the leaf blade is a unique and extensive habitat for microbial communities. Phyllosphere bacteria are the second most closely associated microbial group with plants after fungi and viruses, and are the most abundant, occupying a dominant position in the phyllosphere microbial community. Host species are a major factor influencing the community diversity and structure of phyllosphere microorganisms. Methods: In this study, six Populus spp. were selected for study under the same site conditions and their phyllosphere bacterial community DNA fragments were paired-end sequenced using 16S ribosomal RNA (rRNA) gene amplicon sequencing. Based on the distribution of the amplicon sequence variants (ASVs), we assessed the alpha-diversity level of each sample and further measured the differences in species abundance composition among the samples, and predicted the metabolic function of the community based on the gene sequencing results. Results: The results revealed that different Populus spp. under the same stand conditions resulted in different phyllosphere bacterial communities. The bacterial community structure was mainly affected by the carbon and soluble sugar content of the leaves, and the leaf nitrogen, phosphorus and carbon/nitrogen were the main factors affecting the relative abundance of phyllosphere bacteria. Discussion: Previous studies have shown that a large proportion of the variation in the composition of phyllosphere microbial communities was explained by the hosts themselves. In contrast, leaf-borne nutrients were an available resource for bacteria living on the leaf surface, thus influencing the community structure of phyllosphere bacteria. These were similar to the conclusions obtained in this study. This study provides theoretical support for the study of the composition and structure of phyllosphere bacterial communities in woody plants and the factors influencing them.