Characterization, expression, and functional analysis of the pathogenesis-related gene PtDIR11 in transgenic poplar.

Lignins and lignans are important for plant resistance to pathogens. Dirigent (DIR) proteins control the regio- and stereo-selectivity of coniferyl alcohol in lignan and lignin biosynthesis. DIR genes have been implicated in defense-related responses in several plant species, but their role in poplar immunity is unclear. We cloned PtDIR11 from Populus trichocarpa; we found that overexpression of PtDIR11 in poplar improved the lignan biosynthesis and enhanced the resistance of poplar to Septotis populiperda. PtDIR11 has a typical DIR domain; it belongs to the DIR-b/d family and is expressed in the cell membrane. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis showed that PtDIR11 expression was highest in stems, followed by leaves and roots. Furthermore, PtDIR11 expression was induced by S. populiperda, salicylic acid (SA), jasmonate (JA), and ethylene (ET) stresses. The recombinant PtDIR11 protein inhibited the growth of S. populiperda in vitro. Overexpressing (OE) PtDIR11 in "Nanlin 895" poplar enhanced growth. The OE lines exhibited minimal changes in lignin content, but their total lignan and flavonoid contents were significantly greater than in the wild-type (WT) lines. Overexpression of PtDIR11 affected multiple biological pathways of poplar, such as phenylpropanoid biosynthesis. The methanol extracts of OE-PtDIR11 lines showed greater anti-S. populiperda activity than did lignin extracts from the WT lines. Furthermore, OE-PtDIR11 lines upregulated genes that were related to phenylpropanoid biosynthesis and genes associated with the JA and ET signal transduction pathways; it downregulated genes that were related to SA signal transduction compared with the WT line under S. populiperda stress. Therefore, the OE transgenic plants analysis revealed that PtDIR11 is a good candidate gene for breeding of disease resistant poplar.

[The analysis of differential expression and cloning of genes related to raised secondary lateral veins mutant of Lycoris aurea].

Lycoris aurea exhibits parallel venation, the main vein with many lateral veins in a longitudinal parallel arrangement. There are secondary lateral veins (SLV) between each longitudinal veins. In general, SLVs are not remarkable. In this paper, the material was one kind of Lycoris aurea mutant called Raised Secondary Lateral Veins mutant (RSLV), because many Raised Secondary Lateral Veins are in abaxial surface of its leaves. Its growing potential is weaker than that of wild type and its blades are very thin. Moreover, the stamens of RSLV degenerate completely. Two cDNA libraries were constructed from RSLV mutant and wild type (WT) leaves. From the libraries, 3,122 ESTs, which are longer than 100 bp each after vector sequence removed, were acquired by single-pass sequencing from the 5'end. Following a multistep selection, 512 70-mer oligo-DNA probes were designed for attachment on the microarray slide based on the ESTs. The gene expression profile of RSLV mutant and WT leaves was compared through the microarray at transcriptional level. The microarray experiment results were further confirmed by Quantitative Real-Time PCR (QRT-PCR). We identified 5 genes whose expressions changed more than 2-fold between RSLV mutant and WT leaves. They encode phloem protein 2 (PP2), ferritin, pectin methyl esterase (PME), chlorophyll a/b binding protein (CAB protein) and pyruvate decarboxylase (PDC), respectively. Furthermore, the full-length cDNA sequences of the 5 genes were separately obtained from RSLV and WT by RACE. The relationship between differential expressions of the genes and the formation of the RSLV mutant phenotype were discussed.