Hydrogen peroxide (H2O2) plays important roles in plant development. Adventitious root (AR), lateral bud (LB) and callus formation are important traits for plants. Here, a gene encoding respiratory burst oxidase homologs B (PdeRBOHB) from poplar line “NL895” (Populus. deltoides × P. euramericana) was predicted to be involved in H2O2 accumulation and its reduced expression (RE) transgenic lines were generated. H2O2 content was decreased, and the development of AR, LB and callus was inhibited, in RE PdeRBOHB lines. A gene encoding PdeWRKY75 was identified as the positive upstream transcription factor (TF) for PdeRBOHB. This regulation was confirmed by dual luciferase reporter assay, GUS transient expression analysis and electrophoretic mobility shift assay (EMSA). In the RE PdeWRKY75 lines, H2O2 content was decreased and the development of AR, LB and callus development was inhibited, while in the over expression (OE) lines, H2O2 content was increased and the development of AR and LB was inhibited, but callus formation was enhanced. Additionally, RE PdeRBOHB inhibited the expression of PdeWRKY75, while exogenous application of H2O2 showed the opposite effect. All of these results suggested that PdeWRKY75 and PdeRBOHB are part of a regulatory module in H2O2 accumulation, which is involved in the regulation of multiple biological processes.

The Chinese tallow tree (Triadica sebifera) can produce oil with high content of unsaturated fatty acids in seeds and shows attractive leaf color in autumn and winter. Here, the 739 Mb chromosome-scale genome sequence of the Chinese tallow tree was assembled and it reveals the Chinese tallow tree is a tetraploid. Numerous genes related to nutrition assimilation, energy utilization, biosynthesis of secondary metabolites and resistance significantly expanded or are specific to the Chinese tallow tree. These genes would enable the Chinese tallow tree to obtain high adaptability. More genes in fatty acids biosynthesis in its genome, especially for unsaturated fatty acids biosynthesis, and higher expression of these genes in seeds would be attributed to its high content of unsaturated fatty acids. Cyanidin 3-O-glucoside was identified as the major component of anthocyanin in red leaves. All structural genes in anthocyanin biosynthesis show significantly higher expression in red leaves than in green leaves. Transcription factors, seven MYB and one bHLH, were predicted to regulate these anthocyanin biosynthesis genes. Collectively, we provided insight into the polyploidization, high adaptability and biosynthesis of the high content of unsaturated fatty acids in seeds and anthocyanin in leaves for the Chinese tallow tree.

No abstract

Phosphorus (P) is an important nutrient for plants. Here, we identify a WRKY transcription factor (TF) in poplar (Populus deltoides 3 Populus euramericana) (PdeWRKY65) that modulates tissue phosphate (Pi) concentrations in poplar. PdeWRKY65 overexpression (OE) transgenic lines showed reduced shoot Pi concentrations under both low and normal Pi availabilities, while PdeWRKY65 reduced expression (RE) lines showed the opposite phenotype. A gene encoding a Pi transporter (PHT), PdePHT1;9, was identified as the direct downstream target of PdeWRKY65 by RNA sequencing (RNA-Seq). The negative regulation of PdePHT1;9 expression by PdeWRKY65 was confirmed by DNA-protein interaction assays, including yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), co-expression of the promoters of PdePHT1;9 and PdeWRKY65 in tobacco (Nicotiana benthamiana) leaves, and chromatin immunoprecipitation-quantitative PCR. A second WRKY TF, PdeWRKY6, was subsequently identified and confirmed to positively regulate the expression of PdePHT1;9 by DNA-protein interaction assays. PdePHT1;9 and PdeWRKY6 OE and RE poplar transgenic lines were used to confirm their positive regulation of shoot Pi concentrations, under both normal and low Pi availabilities. No interaction between PdeWRKY6 and PdeWRKY65 was observed at the DNA or protein levels. Collectively, these data suggest that the low Pi-responsive TFs PdeWRKY6 and PdeWRKY65 independently regulate the expression of PHT1;9 to modulate tissue Pi concentrations in poplar.