Genome-Wide Characterization of Dirigent Proteins in Populus: Gene Expression Variation and Expression Pattern in Response to Marssonina brunnea and Phytohormones

Abstract

Marssonina brunnea causes a major disease that limits poplar growth. Lignin and lignan play essential roles in protecting plants from various biological stresses. Dirigent (DIR) proteins are thought to control the stereoselective coupling of coniferyl alcohol in the formation of lignan and lignin. DIR family members have been well studied in several plant species, but no previous detailed genome-wide analysis has been carried out in forest trees, such as poplar. We identified 40 PtDIR genes in Populus trichocarpa and classified them into three subgroups (DIR-a, DIR-b/d, and DIR-e) based on phylogenetic analyses. These genes are distributed on 11 poplar chromosomes, and 80% of PtDIRs (32/40) are intronless. The cis-element analysis inferred that PtDIRs possess many types of biological and abiotic stress-response cis-elements. We also analyzed intra- and inter-specific collinearity, which provided deep insights into the evolutionary characteristics of the poplar DIR genes. Analyses of the protein tertiary structure and critical amino acid residues showed that PtDIR7–10 and PtDIR13–16, which belong to the DIR-a subfamily, might be involved in the regio- and stereo-selectivity of bimolecular phenoxy radical coupling in poplars. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) analysis revealed different expression patterns for the PtDIR genes of P. trichocarpa and the PeDIR genes of ‘Nanlin 895’ in various tissues. Additionally, we analyzed responses of PeDIRs to M. brunnea and different phytohormone treatments (abscisic acid, salicylic acid, methyl jasmonate, and ethylene) in ‘Nanlin 895’. The results showed that at least 18 genes responded strongly to M. brunnea, and these PeDIRs also showed significant responses to phytohormones. These results suggest that DIR genes are involved in the poplar defense response against M. brunnea, and this study will provide fundamental insights for future research on poplar DIR genes.

Transcriptome analysis of trembling aspen (Populus tremuloides) under nickel stress

“…Likewise, Li et al . [ 59 ] identified PtDIR and PeDIR genes that were differentially expressed in Populus trichocarpa in response to Marssonina brunnea and Phytohormones ((abscisic acid, salicylic acid, methyl jasmonate, and ethylene). The heatmap analysis in the present study revealed that none of these common genes was among the top 100 up or downregulated in P .…”

Identification and functional characterization of the dirigent gene family in Phryma leptostachya and the contribution of PlDIR1 in lignan biosynthesis

“…For example, 35 DIRs have been identified in spruce (Picea spp.) [ 21 ], 25 DIRs in Arabidopsis [ 21 ], 19 DIRs in I. indigotica [ 27 ], 27 DIRs in B. rapa [ 28 ], 49 DIRs in O. sativa [ 26 ], 35 DIRs in Chinese White Pear ( Pyrus bretschneideri ) [ 47 ], 44 DIRs in flax ( L. usitatissimum ) [ 25 ], 24 DIRs in pepper ( Capsicum annuum L.) [ 48 ], 45 DIRs in M. truncatula [ 24 ], 40 DIRs in Populus trichocarpa [ 49 ], 54 DIRs in soybean ( Glycine max ) [ 50 ] and 112 DIRs in Cucurbitaceae [ 51 ]. P. leptostachya is an important insecticidal plant and possesses essential insecticidal active ingredients (lignans), the characterization of P. leptostachya DIR genes would benefit the analysis of the formation process of lignan biosynthesis and stress defense in P. leptostachya .…”

“…A recent study also showed that, except for PnDIR5 , F. solani and four signaling molecules (MeJA, SA, ETH, and H 2 O 2 ) influenced PnDIRs’ transcription [ 40 ]. In addition, at least 18 PeDIR genes in the ‘Nanlin 895’ poplar responded substantially to Marssonina brunnea , and these PeDIRs also showed significant responses to the application of phytohormones (ABA, MeJA, SA, ETH) [ 49 ]. In the current study, to find out the hormone response patterns of PlDIRs , the transcript abundance of 15 PlDIRs in response to MeJA, SA, and ETH treatments was analyzed in P. leptostachya roots and leaves (Figs.…”

Residual effect of defeated stripe rust resistance genes/QTLs in bread wheat against prevalent pathotypes of Puccinia striiformis f. sp. tritici

“…The dirigent proteins (DIR) proteins also play essential roles in guiding the correct formation of lignin. Lignin is an important component of the cell wall and is essential in resistance to adverse external environments and provides a physical barrier for healthy plant growth [42,43]. The synthesis of terpenes by terpene synthase is one of the responses to attack in numerous plant-pathogen binomials, where terpenes act as specialized or generalized pathogen inhibitors [44].…”