Genome-wide identification of the WRKY gene family in Camellia oleifera and expression analysis under phosphorus deficiency.

Camellia oleifera Abel. is an economically important woody edible-oil species that is mainly cultivated in hilly areas of South China. The phosphorus (P) deficiency in the acidic soils poses severe challenges for the growth and productivity of C. oleifera. WRKY transcription factors (TFs) have been proven to play important roles in biological processes and plant responses to various biotic/abiotic stresses, including P deficiency tolerance. In this study, 89 WRKY proteins with conserved domain were identified from the C. oleifera diploid genome and divided into three groups, with group II further classified into five subgroups based on the phylogenetic relationships. WRKY variants and mutations were detected in the gene structure and conserved motifs of CoWRKYs. Segmental duplication events were considered as the primary driver in the expanding process of WRKY gene family in C. oleifera. Based on transcriptomic analysis of two C. oleifera varieties characterized with different P deficiency tolerances, 32 CoWRKY genes exhibited divergent expression patterns in response to P deficiency stress. qRT-PCR analysis demonstrated that CoWRKY11, -14, -20, -29 and -56 had higher positive impact on P-efficient CL40 variety compared with P-inefficient CL3 variety. Similar expression trends of these CoWRKY genes were further observed under P deficiency with longer treatment period of 120d. The result indicated the expression sensitivity of CoWRKYs on the P-efficient variety and the C. oleifera cultivar specificity on the P deficiency tolerance. Tissue expression difference showed CoWRKYs may play a crucial role in the transportation and recycling P in leaves by affecting diverse metabolic pathways. The available evidences in the study conclusively shed light on the evolution of the CoWRKY genes in C. oleifera genome and provided a valuable resource for further investigation of functional characterization of WRKY genes involved to enhance the P deficiency tolerance in C. oleifera.

Characterization of the complete plastid genome sequence of Breynia fruticosa (L.) Müll.Arg. (Phyllanthaceae), a traditional Chinese medicine plant.

Breynia fruticosa (L.) Müll.Arg. is a well-known folk medicinal plant and found abundantly in South China. The complete chloroplast genome of B. fruticosa reported firstly here was 155,630 bp in length, including a large single-copy region with 85,065 bp (LSC), a small single-copy region with 19,441 bp (SSC) and a pair of inverted repeats with 25, 562 bp (IRa and IRb). The plastome was comprised of 112 distinct genes, with 78 protein coding genes, four ribosomal RNA genes and 30 transfer RNA genes. The overall GC content of B. fruticose chloroplast genome was 36.7%. Phylogenetic analysis revealed that B. fruticosa was closely related to Glochidion fruticosa.