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Wheat is the most widely grown crop and represents the staple food for one third of the world&rsquo, s population. Wheat is attacked by a large variety of pathogens and the use of resistant cultivars is an effective and environmentally safe strategy for controlling diseases and eliminating the use of fungicides. In this study, a collection of wild and cultivated tetraploid wheats (Triticum turgidum) were evaluated for seedling resistance (SR) and adult plant resistance (APR) to powdery mildew (Blumeria graminis) and genotyped with a 90K single nucleotide polymorphism (SNP) array to identify new sources of resistance genes. The genome-wide association mapping detected 18 quantitative trait loci (QTL) for APR and 8 QTL for SR, four of which were identical or at least closely linked to four QTL for APR. Thirteen candidate genes, containing nucleotide binding sites and leucine-rich repeats, were localized in the confidence intervals of the QTL-tagging SNPs. The marker IWB6155, associated to QPm.mgb-1AS, was located within the gene TRITD1Av1G004560 coding for a disease resistance protein. While most of the identified QTL were described previously, five QTL for APR (QPm.mgb-1AS, QPm.mgb-2BS, QPm.mgb-3BL.1, QPm.mgb-4BL, QPm.mgb-7BS.1) and three QTL for SR (QPm.mgb-3BL.3, QPm.mgb-5AL.2, QPm.mgb-7BS.2) were mapped on chromosome regions where no resistance gene was reported before. The novel QTL/genes can contribute to enriching the resistance sources available to breeders.

The cyclic nucleotide cAMP (3′,5′-cyclic adenosine monophosphate) is nowadays recognised as an important signalling molecule in plants, involved in many molecular processes, including sensing and response to biotic and abiotic environmental stresses. The validation of a functional cAMP-dependent signalling system in higher plants has spurred a great scientific interest on the polyhedral role of cAMP, as it actively participates in plant adaptation to external stimuli, in addition to the regulation of physiological processes. The complex architecture of cAMP-dependent pathways is far from being fully understood, because the actors of these pathways and their downstream target proteins remain largely unidentified. Recently, a genetic strategy was effectively used to lower cAMP cytosolic levels and hence shed light on the consequences of cAMP deficiency in plant cells. This review aims to provide an integrated overview of the current state of knowledge on cAMP’s role in plant growth and response to environmental stress. Current knowledge of the molecular components and the mechanisms of cAMP signalling events is summarised.

Cyclic AMP plays important roles in different physiological processes, including plant defence responses. However, as little information is known on plant enzymes responsible for cAMP production/degradation, studies of cAMP functions have relied, to date, on non-specific pharmacological approaches. We therefore developed a more reliable approach, producing transgenic Arabidopsis thaliana lines overexpressing the 'cAMP-sponge' (cAS), a genetic tool that specifically buffers cAMP levels. In response to an avirulent strain of Pseudomonas syringae pv. tomato (PstAvrB), cAS plants showed a higher bacterial growth and a reduced hypersensitive cell death in comparison with wild-type (WT) plants. The low cAMP availability after pathogen infection delayed cytosolic calcium elevation, as well as hydrogen peroxide increase and induction of redox systems. The proteomic analysis, performed 24 h post-infection, indicated that a core of 49 proteins was modulated in both genotypes, while 16 and 42 proteins were uniquely modulated in WT and cAS lines, respectively. The involvement of these proteins in the impairment of defence response in cAS plants is discussed in this paper. Moreover, in silico analysis revealed that the promoter regions of the genes coding for proteins uniquely accumulating in WT plants shared the CGCG motif, a target of the calcium-calmodulin-binding transcription factor AtSR1 (Arabidopsis thaliana signal responsive1). Therefore, following pathogen perception, the low free cAMP content, altering timing and levels of defence signals, and likely acting in part through the mis-regulation of AtSR1 activity, affected the speed and strength of the immune response.

Flavonoids are a well-studied group of secondary metabolites, belonging to the phenylpropanoid pathway. Flavonoids are known to exhibit health promoting effects such as antioxidant capacities, anti-cancer and anti-inflammatory activity. Globe artichoke is an important source of bioactive phenolic compounds, including flavonoids. To study the regulation of their biosynthesis, a R2R3-MYB transcription factor, CcMYB12, was isolated from artichoke leaves. Phylogenetic analysis showed that this protein belongs to the MYB subgroup 7 (flavonol-specific MYB), which includes Arabidopsis AtMYB12, grapevine VvMYBF1, and tomato SlMYB12. CcMYB12 transcripts were detected specifically in artichoke immature inflorescence and young leaves and overlapped with the profiles of flavonol biosynthetic genes. Electrophoretic mobility shift assays (EMSAs) revealed that recombinant CcMYB12 protein is able to bind to ACII element, a DNA binding site ubiquitously present in the promoters of genes encoding flavonol biosynthetic enzymes. In transgenic Arabidopsis plants, the overexpression of CcMYB12 activated the expression of endogenous flavonol biosynthesis genes, leading to an increase of flavonol accumulation and a decrease of anthocyanins in leaves. Likewise, in transgenic tobacco petals and leaves, the overexpression of CcMYB12 decreased anthocyanin levels and increased flavonols.

Exploiting the biodiversity of crops and their wild relatives is fundamental for maintaining and increasing food security. The species Cynara cardunculus includes three taxa: the globe artichoke, one of the most important Mediterranean vegetables, the leafy cardoon, and the wild cardoon. In this study, genotyping by sequencing (GBS) was successfully applied to reveal thousands of polymorphisms in a C. cardunculus germplasm collection, including 65 globe artichoke, 9 leafy cardoon, and 21 wild cardoon samples. The collection showed a strong population structure at K = 2, separating the globe artichoke from the leafy and wild cardoon. At higher K values, further substructures were observed, in which the wild cardoon was separated from the leafy cardoon, and the latter included the Spanish wild cardoons, while the wild sample from Portugal was admixed. Moreover, subpopulations within the globe artichoke set were highlighted. Structure analysis restricted to the globe artichoke dataset pointed out genetic differentiation between the ˝Catanesi˝ typology and all the other samples (K = 2). At higher values of K, the separation of the ˝Catanesi˝ group still held true, and green headed landraces from Apulia region, Italy (˝Green Apulian˝) formed a distinct subpopulation. ˝Romaneschi˝ artichoke types fell in a variable group with admixed samples, indicating that they should not be considered as a genetically uniform typology. The results of principal component analysis and Neighbor-Joining hierarchical clustering were consistent with structure results, and in addition provided a measure of genetic relationships among individual genotypes. Both analyses attributed the wild material from Spain and Portugal to the cultivated cardoon group, supporting the idea that this might be indeed a feral form of the leafy cardoon. Different reproductive habit and possibly selective pressure led to a slower LD decay in artichoke compared to cardoon. Genotyping by sequencing has proven a reliable methodology to obtain valuable SNPs and assess population genetics in C. cardunculus.

Phenolic acids are major components of cell walls in wheat and have important implications on human health as antioxidants with anti-tumor activity. Our objectives were to identify phenolic acid genes in wheat by single nucleotide polymorphisms (SNPs) detected within the coding sequences of candidate genes, and to identify chromosomal regions associated with single phenolic acids and total soluble phenolic compounds. A set of candidate genes involved in the biosynthesis of hydroxycinnamic acid derivatives were identified by comparative genomics. SNPs found in the coding sequences of six genes (PAL1, PAL2, C4H, C3H, COMT1 and COMT2) were used to determine their chromosomal location and accurate map position on two reference consensus linkage maps. The genome-wide association study (GWAS), based on genotyping a tetraploid wheat collection with 81,587 gene-associated SNPs, detected 22 quantitative trait loci (QTL) distributed on almost all durum wheat chromosomes. Two QTL for p-coumaric acid were coincident with the phenylalanine ammonia-lyase (PAL2) and p-coumarate 3-hydroxylase (C3H) genes on chromosome arms 2AL and 1AL, respectively. The availability of candidate gene-based markers can allow elucidating the mechanism of phenolic acids accumulation in wheat kernels and exploiting the genetic variability of phenolic acids content for the nutritional improvement of wheat end-products.

Cyclic adenosine 3',5'-monophosphate (cAMP) is a recognized second messenger; however, knowledge of cAMP involvement in plant physiological processes originates primarily from pharmacological studies. To obtain direct evidence for cAMP function in plants, tobacco Bright Yellow-2 (BY-2) cells were transformed with the cAMP sponge, which is a genetically encoded tool that reduces cAMP availability. BY-2 cells expressing the cAMP sponge (cAS cells), showed low levels of free cAMP and exhibited growth inhibition that was not proportional to the cAMP sponge transcript level. Growth inhibition in cAS cells was closely related to the precocious inhibition of mitosis due to a delay in cell cycle progression. The cAMP deficiency also enhanced antioxidant systems. Remarkable changes occurred in the cAS proteomic profile compared with that of wild-type (WT) cells. Proteins involved in translation, cytoskeletal organization, and cell proliferation were down-regulated, whereas stress-related proteins were up-regulated in cAS cells. These results support the hypothesis that BY-2 cells sense cAMP deficiency as a stress condition. Finally, many proteasome subunits were differentially expressed in cAS cells compared with WT cells, indicating that cAMP signaling broadly affects protein degradation via the ubiquitin/proteasome pathway.

The infection of Arabidopsis thaliana plants with avirulent pathogens causes the accumulation of cGMP with a biphasic profile downstream of nitric oxide signalling. However, plant enzymes that modulate cGMP levels have yet to be identified, so we generated transgenic A. thaliana plants expressing the rat soluble guanylate cyclase (GC) to increase genetically the level of cGMP and to study the function of cGMP in plant defence responses. Once confirmed that cGMP levels were higher in the GC transgenic lines than in wild-type controls, the GC transgenic plants were then challenged with bacterial pathogens and their defence responses were characterized. Although local resistance was similar in the GC transgenic and wild-type lines, differences in the redox state suggested potential cross-talk between cGMP and the glutathione redox system. Furthermore, large-scale transcriptomic and proteomic analysis highlighted the significant modulation of both gene expression and protein abundance at the infection site, inhibiting the establishment of systemic acquired resistance. Our data indicate that cGMP plays a key role in local responses controlling the induction of systemic acquired resistance in plants challenged with avirulent pathogens.