Identification of quantitative trait loci affecting ectomycorrhizal symbiosis in an interspecific F1 poplar cross and differential expression of genes in ectomycorrhizas of the two parents: Populus deltoides and Populus trichocarpa

Abstract

A Populus deltoides×Populus trichocarpa F 1 pedigree was analyzed for quantitative trait loci (QTLs) affecting ectomycorrhizal development and for microarray characterization of gene networks involved in this symbiosis. A 300 genotype progeny set was evaluated for its ability to form ectomycorrhiza with the basidiomycete Laccaria bicolor. The percentage of mycorrhizal root tips was determined on the root systems of all 300 progeny and their two parents. QTL analysis identified four significant QTLs, one on the P. deltoides and three on the P. trichocarpa genetic maps. These QTLs were aligned to the P. trichocarpa genome and each contained several megabases and encompass numerous genes. NimbleGen whole-genome microarray, using cDNA from RNA extracts of ectomycorrhizal root tips from the parental genotypes P. trichocarpa and P. deltoides, was used to narrow the candidate gene list. Among the 1,543 differentially expressed genes (p value ≤ 0.05; ≥5.0-fold change in transcript level) having different transcript levels in mycorrhiza of the two parents, 41 transcripts were located in the QTL intervals: 20 in Myc_d1, 14 in Myc_t1, and seven in Myc_t2, while no significant differences among transcripts were found in Myc_t3. Among these 41 transcripts, 25 were overrepresented in P. deltoides relative to P. trichocarpa; 16 were overrepresented in P. trichocarpa. The transcript showing the highest overrepresentation in P. trichocarpa mycorrhiza libraries compared to P. deltoides mycorrhiza codes for an ethylene-sensitive EREBP-4 protein which may repress defense mechanisms in P. trichocarpa while the highest overrepresented transcripts in P. deltoides code for proteins/genes typically associated with pathogen resistance.

Ectomycorrhizal Colonization and Diversity in Relation to Tree Biomass and Nutrition in a Plantation of Transgenic Poplars with Modified Lignin Biosynthesis

“…Therefore, each transformation event may cause intra-specific variation of traits, in addition to the target gene. Controlled experiments testing the colonization efficiency of the EM fungus Laccaria bicolor with the F1 progeny of an inter-specific poplar hybrid revealed that the ability to form mycorrhizas underlies natural intra-specific variation [55]–[57]. Different EM assemblages were also observed in the present study for different varieties of P .…”

Plant genetic effects on soils under climate change

“…In some cases, these community changes are associated with relatively small changes in root traits and likely numbers of genes (e.g., Bressan et al 2009;Lankau 2011), though recent studies indicate that most traits are controlled by many genes (Mackay et al 2009). A recently discovered quantitative trait locus (QTL) in Populus spp affects ectomycorrhizal symbiosis (Labbe et al 2011), suggesting sensitivity of belowground symbioses to tree genetics similar to traditional plant traits such as productivity, chemistry, and wateruse. Similar sensitivity of other components of the rhizosphere community to plant genetic variation remain understudied in natural systems, but are important to consider since climate change factors which favor higher belowground C allocation (e.g., drought, high atmospheric CO 2 ) are likely to favor genotypes with higher investment in rhizosphere symbioses (e.g., Table 1).…”

The obscure events contributing to the evolution of an incipient sex chromosome in Populus: a retrospective working hypothesis

“…Moreover, with a large root system maintaining water and P. deltoides Female 1,991.7 (145.6) 100.9 (13.9) 31.6 (4.2) 13.8 (1.6) 37.5 (6.0) 10.7 (3.8) 32.3 (6.7) P. nigra As determined by gas chromatography-mass spectrometry; retention time and key m/z are shown at the column headings; mean and SEM () of two male to six female replicate buds are shown within rows nutrient uptake and functioning to facilitate interannual store of carbon over multiple decades, the selective pressure to develop symbiotic interactions with soil microflora may be as strong as to develop pathogenic resistances. As an illustration, various loci controlling variation for both symbiosis levels and resistance have been identified in Populus (Zhang et al 2001;Yin et al 2004b;Jorge et al 2005;Tagu et al 2005;Kohler et al 2008;Duplessis et al 2009;Labbé et al 2011). Plants, in general, and Populus, in particular, have a variety of disease resistance genes (R) encoding proteins involved in the detection of pathogens and herbivores.…”