Analysis of Xylem Cells by Nucleus-Based Transcriptomics and Chromatin Profiling.

Nuclei contain essential information for cell states, including chromatin and RNA profiles - features which are nowadays accessible using high-throughput sequencing applications. Here, we describe analytical pipelines including nucleus isolation from differentiated xylem tissues by fluorescence-activated nucleus sorting (FANS), as well as subsequent SMART-seq2-based transcriptome profiling and assay for transposase-accessible chromatin (ATAC)-seq-based chromatin analysis. Combined with tissue-specific expression of nuclear fluorescent reporters, these pipelines allow obtaining tissue-specific data on gene expression and on chromatin structure and are applicable for a large spectrum of cell types, tissues, and organs. Considering, however, the extreme degree of differentiation found in xylem cells with programmed cell death happening during vessel element formation and their role as a long-term depository for atmospheric CO2 in the form of wood, xylem cells represent intriguing and relevant objects for large-scale profilings of their cellular signatures.

OBERON3 and SUPPRESSOR OF MAX2 1-LIKE proteins form a regulatory module driving phloem development.

Spatial specificity of cell fate decisions is central for organismal development. The phloem tissue mediates long-distance transport of energy metabolites along plant bodies and is characterized by an exceptional degree of cellular specialization. How a phloem-specific developmental program is implemented is, however, unknown. Here we reveal that the ubiquitously expressed PHD-finger protein OBE3 forms a central module with the phloem-specific SMXL5 protein for establishing the phloem developmental program in Arabidopsis thaliana. By protein interaction studies and phloem-specific ATAC-seq analyses, we show that OBE3 and SMXL5 proteins form a complex in nuclei of phloem stem cells where they promote a phloem-specific chromatin profile. This profile allows expression of OPS, BRX, BAM3, and CVP2 genes acting as mediators of phloem differentiation. Our findings demonstrate that OBE3/SMXL5 protein complexes establish nuclear features essential for determining phloem cell fate and highlight how a combination of ubiquitous and local regulators generate specificity of developmental decisions in plants.

Are Peach Cultivars Used in Conventional Long Food Supply Chains Suitable for the High-Quality Short Markets?

Peaches are climacteric and highly perishable fruits, with a short shelf life, and are prone to rapid deterioration after harvest. In this study, the chemical proprieties, aroma profile and a sensory evaluation were conducted to: (1) characterize and compare fruits of 13 different peach and nectarine cultivars, harvested at physiological maturation; and (2) assess the suitability of these cultivars, that are successfully used in long food supply chains (LFSCs), for their use in short food supply chains (SFSCs). Through statistical analysis clear differences were found among the studied cultivars, and in particular between cultivars suited to SFSCs compared to those suited for LFSCs. Results indicate that, despite all cultivars being planted in the same orchards and with the same pre-harvest management and practices, their post-harvest performances were mainly influenced by the cultivar genetic makeup. Therefore, cultivars conventionally used in SFSCs, such as "Guglielmina" and "Regina di Londa", had the best aroma, sweetness and juiciness compared to LSCPs ones. In contrast, the LSCPs varieties showed interesting values for firmness and crunchiness.