Root diameter, a critical indicator of root physiological function, varies greatly among tree species, but the underlying mechanism of this high variability is unclear. Here, we sampled 50 tree species across tropical and temperate zones in China, and measured root morphological and anatomical traits along the first five branch orders in each species. Our objectives were (i) to reveal the relationships between root diameter, cortical thickness and stele diameter among tree species in tropical and temperate forests, and (ii) to investigate the relationship of both root morphological and anatomical traits with divergence time during species radiation. The results showed that root diameter was strongly affected by cortical thickness but less by stele diameter in both tropical and temperate species. Changes in cortical thickness explained over 90% of variation in root diameter for the first order, and ∼74-87% for the second and third orders. Thicker roots displayed greater cortical thickness and more cortical cell layers than thinner roots. Phylogenetic analysis demonstrated that root diameter, cortical thickness and number of cortical cell layers significantly correlated with divergence time at the family level, showing similar variation trends in geological time. The results also suggested that trees tend to decrease their root cortical thickness rather than stele diameter during species radiation. The close linkage of variations in root morphology and anatomy to phylogeny as demonstrated by the data from the 50 tree species should provide some insights into the mechanism of root diameter variability among tree species.

It is thought that fungi protect themselves from predation by the production of compounds that are toxic to soil-dwelling animals. Here, we show that a nontoxic pigment, the bis-naphthopyrone aurofusarin, protects Fusarium fungi from a wide range of animal predators. We find that springtails (primitive hexapods), woodlice (crustaceans), and mealworms (insects) prefer feeding on fungi with disrupted aurofusarin synthesis, and mealworms and springtails are repelled by wheat flour amended with the fungal bis-naphthopyrones aurofusarin, viomellein, or xanthomegnin. Predation stimulates aurofusarin synthesis in several Fusarium species and viomellein synthesis in Aspergillus ochraceus . Aurofusarin displays low toxicity in mealworms, springtails, isopods, Drosophila , and insect cells, contradicting the common view that fungal defence metabolites are toxic. Our results indicate that bis-naphthopyrones are defence compounds that protect filamentous ascomycetes from predators through a mechanism that does not involve toxicity.

Long-read RNA sequencing (RNA-seq) holds great potential for characterizing transcriptome variation and full-length transcript isoforms, but the relatively high error rate of current long-read sequencing platforms poses a major challenge. We present ESPRESSO, a computational tool for robust discovery and quantification of transcript isoforms from error-prone long reads. ESPRESSO jointly considers alignments of all long reads aligned to a gene and uses error profiles of individual reads to improve the identification of splice junctions and the discovery of their corresponding transcript isoforms. On both a synthetic spike-in RNA sample and human RNA samples, ESPRESSO outperforms multiple contemporary tools in not only transcript isoform discovery but also transcript isoform quantification. In total, we generated and analyzed ~1.1 billion nanopore RNA-seq reads covering 30 human tissue samples and three human cell lines. ESPRESSO and its companion dataset provide a useful resource for studying the RNA repertoire of eukaryotic transcriptomes.

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