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A newly documented pathotype 5 of the soil-borne fungus Sporisorium reilianum, causing head smut in sorghum, was tested against 153 unexplored Senegalese sorghum accessions. Among the 153 sorghum accessions tested, 63 (41%) exhibited complete resistance, showing no signs of infection by the fungus. The remaining 90 accessions (59%) displayed varying degrees of susceptibility. Sorghum responses against S. reilianum were explored to analyze the potential link with previously known seed morphology-related traits and new phenotype data from 59 lines for seed weight. A genome-wide association study (GWAS) screened 297,876 SNPs and identified highly significant associations (p < 1 × 10−5) with head smut resistance in sorghum. By mapping these significant SNPs to the reference genome, this study revealed 35 novel candidate defense genes potentially involved in disease resistance. [ABSTRACT FROM AUTHOR]

Premise: Despite myriad examples of local adaptation, the phenotypes and genetic variants underlying such adaptive differentiation are seldom known. Recent work on freezing tolerance and local adaptation in ecotypes of Arabidopsis thaliana from Italy and Sweden provides an essential foundation for uncovering the genotype–phenotype–fitness map for an adaptive response to a key environmental stress. Methods: We examined the consequences of a naturally occurring loss‐of‐function (LOF) mutation in an Italian allele of the gene that encodes the transcription factor CBF2, which underlies a major freezing‐tolerance locus. We used four lines with a Swedish genetic background, each containing a LOF CBF2 allele. Two lines had introgression segments containing the Italian CBF2 allele, and two contained deletions created using CRISPR‐Cas9. We used a growth chamber experiment to quantify freezing tolerance and gene expression before and after cold acclimation. Results: Freezing tolerance was lower in the Italian (11%) compared to the Swedish (72%) ecotype, and all four experimental CBF2 LOF lines had reduced freezing tolerance compared to the Swedish ecotype. Differential expression analyses identified 10 genes for which all CBF2 LOF lines, and the IT ecotype had similar patterns of reduced cold responsive expression compared to the SW ecotype. Conclusions: We identified 10 genes that are at least partially regulated by CBF2 that may contribute to the differences in cold‐acclimated freezing tolerance between the Italian and Swedish ecotypes. These results provide novel insight into the molecular and physiological mechanisms connecting a naturally occurring sequence polymorphism to an adaptive response to freezing conditions. [ABSTRACT FROM AUTHOR]

The plant hormone auxin regulates various growth and developmental processes by controlling the expression of auxin-response genes. While many genes up-regulated by auxin have been characterized, less is known about the genes that are down-regulated by auxin. We isolated and characterized an auxin-repressed gene (RpARP) from the tree legume, Robinia pseudoacacia L. A sequence similarity search in public databases showed that the RpARP gene has homologs in various higher plants including monocots and dicots. The deduced amino acid sequences are highly conserved among these homologs (up to 85% identity). Northern blot analysis showed that auxin repressed RpARP gene expression and that repression was dependent on the presence of metabolizable sugar and on protein synthesis. In addition, cold treatment abolished the auxin-mediated repression of RpARP gene expression. Results from transgenic plant analyses suggest that RpARP gene expression is posttranscriptionally regulated by auxin and by the untranslated regions. Sequence analysis of the promoter region (-70 and -500 bp upstream of the putative transcription initiation site) of the RpARP gene identified four sucrose-repressible response elements (TATCCAT-motifs; Huang et al. 1990), suggesting that the cis-elements responsible for regulation by sucrose are located in the promoter region. In fact, the expression of the transgenic RpARP gene was unaffected by sucrose when driven by a CaMV 35S promoter. We present evidence that RpARP gene expression is negatively associated with hypocotyl elongation.