Phosphate (Pi) stress-responsive transcription factors PdeWRKY6 and PdeWRKY65 regulate the expression of PdePHT1;9 to modulate tissue Pi concentration in poplar.

Phosphorus (P) is an important nutrient for plants. Here, we identify a WRKY transcription factor (TF) in poplar (Populus deltoides × 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.

Isolation, identification and bioactivity of endophytic fungi from medicinal plant Malus sieboldii.

OBJECTIVE: To isolate and identify endophytic fungi from Malus sieboldii, and detect cytotoxicity, protease inhibition and antifungal activities of their crude extracts. METHOD: The fungi were identified with the aid of morphology or Internal Transcribed Spacer (ITS) rDNA molecular methods. Fungal activities were tested by cylinder-plate, MTT and BRpNA methods, respectively. RESULT: A total of 217 endophytic fungi were isolated from M. sieboldii. Of the 22 taxa obtained, non-sporulating, Alternaria, Colletotrichum, Aspergillu, Fusarlum, Gliocladium and Cunninghamella were dominant communities. The result of the bioactivity test showed that 30 endophytic fungi displayed inhibition against at least one pathogenic fungus, and 3 and 4 showed cytotoxicity and protease inhibition, respectively. CONCLUSION: M. sieboldii should be a potential source of bioactive endophytic fungi.