Formation and Development of Taproots in Deciduous Tree Species

Combining a tunable pinhole with synchronous fluorescence spectrometry for visualization and quantification of benzo[a]pyrene at the root epidermis microstructure of Kandelia obovata

The adsorption of polycyclic aromatic hydrocarbons (PAHs) by mangrove roots and their transport to chloroplasts is a potentially critical process that reduces the carbon sequestration efficiency of mangroves. Yet the crucial initial step, the distribution and retention of PAHs at the root epidermis microstructure, remains unclear. A novel method with a spatial resolution of 311 nm was developed for visualizing and quantifying benzo[a]pyrene (B[a]P) at the root epidermis microstructure (0.096 mm2) of Kandelia obovata (Ko). This method combined a tunable pinhole in laser confocal scanning microscopy with synchronous fluorescence spectrometry to reduce the auto-fluorescence interference in locating B[a]P and improve quantitative sensitivity. The linear range for the established method was 0.44-50.00 ng mm-2, with a detection limit of 0.063 ng mm-2 and a relative standard deviation of 9.45%. In a 60-day hydroponic experiment, B[a]P was primarily adsorbed along the epidermis cell walls of secondary lateral roots and lateral roots, with retained amounts of 0.65 ng mm-2 and 0.49 ng mm-2, respectively. It was found to cluster and predominantly accumulate at the epidermal cell surfaces of taproots (0.24 ng mm-2). B[a]P might enter inner root tissues through the root epidermal cell walls and surfaces of Ko, with the cell walls potentially being the main route. This study potentially provides a pathway for visualizing and quantifying B[a]P entering inner root tissues of mangroves.

Identification of genetics and hormonal factors involved in Quercus robur root growth regulation in different cultivation system

Understanding the molecular processes and hormonal signals that govern root growth is of paramount importance for effective forest management. While Arabidopsis studies have shed light on the role of the primary root in root system development, the structure of root systems in trees is considerably more intricate, posing challenges to comprehend taproot growth in acorn-sown and nursery-cultivated seedlings. In this study, we investigated Quercus robur seedlings using rhizotrons, containers, and transplanted containers to rhizotrons, aiming to unravel the impact of forest nursery practices on processes governing taproot growth and root system development. Root samples were subjected to RNA-seq analysis to identify gene expression patterns and perform differential gene expression and phytohormone analysis. Among studied cultivation systems, differentially expressed genes (DEGs) exhibited significant diversity, where the number of co-occurring DEGs among cultivation systems was significantly smaller than the number of unique DEGs in different cultivation systems. Moreover, the results imply that container cultivation triggers the activation of several genes associated with linolenic acid and peptide synthesis in root growth. Upon transplantation from containers to rhizotrons, rapid enhancement in gene expression occurs, followed by gradual reduction as root growth progresses, ultimately reaching a similar expression pattern as observed in the taproot of rhizotron-cultivated seedlings. Phytohormone analysis revealed that taproot growth patterns under different cultivation systems are regulated by the interplay between auxin and cytokinin concentrations. Moreover, the diversification of hormone levels within the root zone and cultivation systems allows for taproot growth inhibition and prompt recovery in transplanted seedlings. Our study highlights the crucial role of hormone interactions during the early stages of taproot elongation, influencing root system formation across.

OakRootRNADB-a consolidated RNA-seq database for coding and noncoding RNA in roots of pedunculate oak (Quercus robur)

The degree to which roots elongate is determined by the expression of genes that regulate root growth in each developmental zone of a root. Most studies have, however, focused on the molecular factors that regulate primary root growth in annual plants. In contrast, the relationship between gene expression and a specific pattern of taproot development and growth in trees is poorly understood. However, the presence of a deeply located taproot, with branching lateral roots, can especially mitigate the effect of insufficient water availability in long-lived trees, such as pedunculated oak. In the present article, we integrated the ribonucleic acid (RNA) sequencing data on roots of oak trees into a single comprehensive database, named OakRootRNADB that contains information on both coding and noncoding RNAs. The sequences in the database also enclose information pertaining to transcription factors, transcriptional regulators and chromatin regulators, as well as a prediction of the cellular localization of a transcript. OakRootRNADB has a user-friendly interface and functional tools that increase access to genomic information. Integrated knowledge of molecular patterns of expression, specifically occurring within and between root zones and within root types, can elucidate the molecular mechanisms regulating taproot growth and enhanced root soil exploration. Database URL https://oakrootrnadb.idpan.poznan.pl/.