The plant peptide hormone phytosulfokine promotes somatic embryogenesis by maintaining redox homeostasis in Cunninghamia lanceolata.

Somatic embryogenesis (SE) is widely used for studying the mechanisms of embryo development. However, little is known about the underlying mechanisms, especially in woody plants. Previous studies have established an SE system for Chinese fir (Cunninghamia lanceolata), but this system is genotype-dependent, which limits its application in practice. Here, we found that phytosulfokine (PSK), a plant peptide hormone, can not only increase SE efficiency, but also establish SE in recalcitrant genotypes of C. lanceolata. Proembryogenic mass (PEM) browning and determination of hydrogen peroxide (H2 O2 ) content by 2',7'-dichlorofluorescein staining indicated that a reactive oxygen species (ROS) burst occurred rapidly after PEMs were transferred to SE induction medium. Transcriptome analysis and quantitative reverse transcriptase-PCR validation showed that PSK treatment helped to maintain ROS homeostasis by decreasing the activity of peroxidases in early SE induction. This PSK-regulated redox microenvironment might be helpful to induce expression of SE-related genes like WOX2 in early SE induction. Further analyses suggested that PSK promotes SE induction in C. lanceolata partially through decreasing H2 O2 levels, which is necessary but not sufficient for SE induction in recalcitrant genotypes of C. lanceolata. Furthermore, heterologous overexpression of ClPSK in Arabidopsis led to enhanced SE induction and resistance to H2 O2 stress. Taken together, our study reveals a biological function for the plant peptide hormone PSK, extends our knowledge about SE in woody trees, and provides a valuable tool for establishing an efficient and genotype-independent SE system in C. lanceolata and other coniferous trees.

The complete chloroplast genome of Yunnanopilia longistaminea (Opiliaceae), an endemic species in southwest China.

The complete chloroplast genome sequence of Yunnanopilia longistaminea, an endemic species in southwest China, is presented in this study. The total genome size of Y. longistaminea was 148,503 bp in length, with a typical quadripartite structure including a pair of inverted repeat (IRs, 28,075 bp) regions separated by a large single copy (LSC, 84,547bp) region and a small single copy (SSC, 7805 bp) region. The all GC content was 37.3%. The genome contains 117 genes, including 72 protein-coding genes, 37 tRNA genes, and 8 rRNA genes, 13 genes contain a single intron, and 3 genes have two introns. Further, a maximum-likelihood (ML) phylogenetic tree results that Y. longistaminea was closely related to the genera of Champereia manillana.

The complete chloroplast genome of Dipterocarpus turbinatus Gaertn. F.

Dipterocarpus turbinatus Gaertn. F., naturally distributes in Southern China, which is an elite natural tree with high economic and medicinal value. In study, all chloroplast (cp) genome of Dipterocarpus turbinatus Gaertn. F. was assembled and characterized based on Illumina pair-end sequencing data. The complete chloroplast genome length was 152,279 bp. It contained a large (LSC, 83,862 bp) and a small (SSC, 20,215 bp) single copy region, separated by a pair of inverted repeats of 24,101 bp (IRs). The overall GC content of genome was 37.3%, the corresponding values of LSC, SSC, and IR regions were 35.3, 31.6, and 43.2%, respectively. There were 128 genes in the genome including 84 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. Among all genes, 14 genes contain a single intron and 1 gene has two introns. The result showed that Dipterocarpus turbinatus Gaertn. F. was closely related to Vatica mangachapoi.