The coordination of melatonin and anti-bacterial activity by EIL5 underlies ethylene-induced disease resistance in cassava.

Ethylene and melatonin are widely involved in plant development and environmental stress responses. However, the role of their direct relationship in the immune response and the underlying molecular mechanisms in plants remain elusive. Here, we found that Xanthomonas axonopodis pv. manihotis (Xam) infection increased endogenous ethylene levels, which positively modulated plant disease resistance through activating melatonin accumulation in cassava. In addition, the ethylene-responsive transcription factor ETHYLENE INSENSITIVE LIKE5 (MeEIL5), a positive regulator of disease resistance, was essential for ethylene-induced melatonin accumulation and disease resistance in cassava. Notably, the identification of heat stress transcription factor 20 (MeHsf20) as an interacting protein of MeEIL5 indicated the association between ethylene and melatonin in plant disease resistance. MeEIL5 physically interacted with MeHsf20 to promote the transcriptional activation of the gene encoding N-acetylserotonin O-methyltransferase 2 (MeASMT2), thereby improving melatonin accumulation. Moreover, MeEIL5 promoted the physical interaction of MeHsf20 and pathogen-related gene 3 (MePR3), resulting in improved anti-bacterial activity of MePR3. This study illustrates the dual roles of MeEIL5 in fine-tuning MeHsf20-mediated coordination of melatonin biosynthesis and anti-bacterial activity, highlighting the ethylene-responsive MeEIL5 as the integrator of ethylene and melatonin signals in the immune response in cassava.

Single-cell transcriptome sequencing atlas of cassava tuberous root.

Introduction: Single-cell transcriptome sequencing (ScRNA-seq) has emerged as an effective method for examining cell differentiation and development. In non-model plants, it hasn't been employed very much, especially in sink organs that are abundant in secondary metabolites. Results: In this study, we sequenced the single-cell transcriptomes at two developmental phases of cassava tuberous roots using the technology known as 10x Genomics (S1, S2). In total, 14,566 cells were grouped into 15 different cell types, primarily based on the marker genes of model plants known to exist. In the pseudotime study, the cell differentiation trajectory was defined, and the difference in gene expression between the two stages on the pseudotime axis was compared. The differentiation process of the vascular tissue and cerebral tissue was identified by the trajectory. We discovered the rare cell type known as the casparian strip via the use of up-regulated genes and pseudotime analysis, and we explained how it differentiates from endodermis. The successful creation of a protoplast isolation technique for organs rich in starch was also described in our study. Discussion: Together, we created the first high-resolution single-cell transcriptome atlas of cassava tuberous roots, which made significant advancements in our understanding of how these roots differentiate and develop.