Genome-wide association study of 23 f lowering phenology traits and 4 f loral agronomic traits in tree peony (Paeonia section Moutan DC.) reveals five genes known to regulate f lowering time

Tree peony is a unique traditional f lower in China,with large,fragrant,and colorful f lowers.However,a relatively short and concentrated f lowering period limits the applications and production of tree peony.A genome-wide association study(GWAS)was conducted to accelerate molecular breeding for the improvement of f lowering phenology traits and ornamental phenotypes in tree peony.A diverse panel of 451 tree peony accessions was phenotyped for 23 f lowering phenology traits and 4 f loral agronomic traits over 3 years.Genotyping by sequencing(GBS)was used to obtain a large number of genome-wide single-nucleotide polymorphisms(SNPs)(107050)for the panel genotypes,and 1047 candidate genes were identified by association mapping.Eighty-two related genes were observed during at least 2 years for f lowering,and seven SNPs repeatedly identified for multiple f lowering phenology traits over multiple years were highly significantly associated with five genes known to regulate f lowering time.We validated the temporal expression profiles of these candidate genes and highlighted their possible roles in the regulation of f lower bud differentiation and f lowering time in tree peony.This study shows that GWAS based on GBS can be used to identify the genetic determinants of complex traits in tree peony.The results expand our understanding of f lowering time control in perennial woody plants.Identification of markers closely related to these f lowering phenology traits can be used in tree peony breeding programs for important agronomic traits.

Root and xylem ABA changes in response to soil drying in two woody plants

Two woody plants, Platycladus orientalise (tolerant to drought) and Acacia auriculi-formis (sensitive to drought), have been subjected to rapid and slow soil drying. ABA levels in their roots and xylem sap have been determined using radioimmunoassay (RIA, sensitivity is 0.4 pmol per assay vial) with a monoclonal antibody against ( + )-ABA. ABA contents of P. orientalise and A. auriculiformis growing in well watered soil are 0.3 and 2.5 nmol-gDW-1 in

Responses of woody plant root and xylem sap ATP to soil drying

The ATP in roots and xylem sap of two woody plant species, Platycladus orientalis and Acacia auriculiformis, subjected to rapid and slow soil drying has been determined employing firefly luciferase ATP assay method (sensitivity is at 10-12 mol ATP L-1). The ATP levels in the two species were 1.6 nmol. gDW-1 and 0.6 nmol. gDW-1 in roots, and 5.6 μmol·m-3 and 8 μmol ·m-3 in xylem sap, respectively. When plants of P. orientalis and A. auriculiformis were subjected to rapid soil drying, respectively, as soil water content （SWC） decreased from the normal level ( 0.2.5 g·gDW-1) to 0.02 and 0.06 g·gDW-1, separately, plant water potential （ ψ ）dropped to - 4 and - 3.2 MPa, differently, the ATP in roots decreased 99.7% and 42%, respectively. When the rapidly dried soil was watered for up to 6 d, SWC and ψ, were found to recover to their normal levels, but ATP content in roots of P. orientalis and A. auriculiformis recovered by 10% and 23%, respectively. When plants

Relative effects of phylogeny,biological characters and environments on leaf traits in shrub biomes across central Inner Mongolia,China

Aims Understanding the drivers for leaf traits is critical to improving our predictions on ecosystems'responses to global changes.Geographic patterns of leaf traits are shaped by phylogenetic,biological and environmental factors simultaneously.However,till now few studies have examined how these factors influenced leaf traits together,and how their effects differed at the within-and among-site levels.Methods We sampled leaf traits from a 1100 km shrub-biome transect across central Inner-Mongolia,including leaf mass per area(LMA),mass-based photosynthetic rate,nitrogen(N)and phosphorus(P)concentrations.We examined the effects of phylogenetic,biological(height and growth rate)and environmental(climate and soil)fac-tors on leaf traits with mixed-model analyses of variance.Variation partitioning method was used to separate the joint and independent effects of these three types of factors.Important Findings(i)Climate and soil fertility(total or available nutrient concentra-tions)together explained 11.4-41.4%of among-site variations,with remarkable difference among traits.(i)Height and height growth rate together explained 0.4--31.9%of trait variations(mostly among-site variations).Our results could only weakly support the ability of leaf traits as predictors for whole-plant growth.(ii)LMA was negatively related to height,which was consistent with the resource-use strategy hypothesis but incon-sistent with the hypotheses proposed for coexisting trees,suggest-ing that the LMA--height relationship is shaped by rather different mechanisms between the within-and among-communities lev-els.(iv)The variation partitioning analysis showed that,the rela-tionships between leaf traits and biological characters largely reflected the differences in both leaf traits and biological char-acters among species that occupying different sites.The relative importance of phylogenetic,biological and environmental fac-tors differed remarkably among leaf traits,between the within-and among-communities levels,and between different biomes.(v)Our results strongly suggest the necessity of examining the three types of factors simultaneously,and at both the within-and among-communities levels,for a better understanding of the drivers for leaf traits patterns.

Verticillium dahliae Secretory Effector PevD1 Induces Leaf Senescence by Promoting ORE1-Mediated Ethylene Biosynthesis

Leaf senescence,the final stage of leaf development,is influenced by numerous internal and environmental signals.So far,how biotic stresses such as pathogen infection regulate leaf senescence is unclear.Here,we found that the premature leaf senescence caused by a soil-borne vascular fungus Verticillium dahliae in Arabidopsis was impaired by the mutation of a protein elicitor from V.dahliae 1(PevD1).Constitutive or inducible overexpression of PevD1 accelerated Arabidopsis leaf senescence.A senescence-associated NAC transcription factor,ORE1,was targeted by PevD1.PevD1 interacted with and stabilized ORE1 protein by disrupting its interaction with the RING-type ubiquitin E3 ligase NLA.Mutation of ORE1 suppressed the premature senescence caused by overexpressing PevD1.Overexpression of ORE1 or PevD1 led to enhanced ethylene production,and ORE1 mediated PevD1-induced ethylene biosynthesis by directly binding to the ACS6 promoter.Loss-of-function of ACSs suppressed V.dahliae-induced leaf senescence in ORE1-overexpressing plants.Interestingly,PevD1 also interacted with Gossypium hirsutum ORE1(GhORE1),and virus-induced gene silencing of GhORE1 delayed V.dahliae-triggered leaf senescence in cotton,indicative of the existence of a conserved mechanism in plants.Altogether,our study demonstrates that V.dahliae induces leaf senescence by secreting the effector PevD1 to regulate the ORE1-ACS6 cascade,providing new insight into biotic stress-induced senescence in plants.

Regulation of cytokinin biosynthesis using PtRD26pro-IPT module improves drought tolerance through PtARR10-PtYUC4/5-mediated reactive oxygen species removal in Populus

Drought is a critical environmental factor which constrains plant survival and growth.Genetic engineering provides a credible strategy to improve drought tolerance of plants.Here,we generated transgenic poplar lines expressing the isopentenyl transferase gene(IPT)under the driver of Pt RD26 promoter(PtRD26 pro-IPT).Pt RD26 is a senescence and drought-inducible NAC transcription factor.Pt RD26 pro-IPT plants displayed multiple phenotypes,including improved growth and drought tolerance.Transcriptome analysis revealed that auxin biosynthesis pathway was activated in the PtRD26 pro-IPT plants,leading to an increase in auxin contents.Biochemical analysis revealed that ARABIDOPSIS RESPONSE REGULATOR10(PtARR10),one of the type-B ARR transcription factors in the cytokinin pathway,was induced in PtRD26 pro-IPT plants and directly regulated the transcripts of YUCCA4(Pt YUC4)and YUCCA5(PtYUC5),two enzymes in the auxin biosynthesis pathway.Overexpression of PtYUC4 enhanced drought tolerance,while simultaneous silencing of PtYUC4/5 evidently attenuated the drought tolerance of Pt RD26 pro-IPT plants.Intriguingly,Pt YUC4/5 displayed a conserved thioredoxin reductase activity that is required for drought tolerance by deterring reactive oxygen species accumulation.Our work reveals the molecular basis of cytokinin and auxin interactions in response to environmental stresses,and shed light on the improvement of drought tolerance without a growth penalty in trees by molecular breeding.