Functional Analysis of the Ferric Uptake Regulator Gene fur in Xanthomonas vesicatoria.

Iron is essential for the growth and survival of many organisms. Intracellular iron homeostasis must be maintained for cell survival and protection against iron toxicity. The ferric uptake regulator protein (Fur) regulates the high-affinity ferric uptake system in many bacteria. To investigate the function of the fur gene in Xanthomonas vesicatoria (Xv), we generated a fur mutant strain, fur-m, by site-directed mutagenesis. Whereas siderophore production increased in the Xv fur mutant, extracellular polysaccharide production, biofilm formation, swimming ability and quorum sensing signals were all significantly decreased. The fur mutant also had significantly reduced virulence in tomato leaves. The above-mentioned phenotypes significantly recovered when the Xv fur mutation allele was complemented with a wild-type fur gene. Thus, Fur either negatively or positively regulates multiple important physiological functions in Xv

Construction of A GBS-Based High-Density Genetic Map and Flower Color-Related Loci Mapping in Grasspea (Lathyrus sativus L.)

Grasspea (Lathyrus sativus L.), a legume crop with excellent resistance to a broad array of environmental stressors, has, to this point, been poorly genetically characterized. High-density genetic linkage maps are critical for draft genome assembly, quantitative trait loci (QTLs) analysis, and gene mining. The lack of a high-density genetic linkage map has limited both genomic studies and selective breeding in grasspea. Here, we developed a high-density genetic linkage map of grasspea using genotyping-by-sequencing (GBS) to sequence 154 grasspea plants, comprising 2 parents and 152 F2 progeny. In all, 307.74 Gb of data was produced, including 2,108,910,938 paired-end reads, as well as 3536 SNPs mapped to seven linkage groups (LG1–LG7). With an average length of 996.52 cM per LG, the overall genetic distance was 6975.68 cM. Both the χ2 test and QTL analysis, based on the Kruskal–Wallis (KW) test and interval mapping (IM) analysis, revealed the monogenic inheritance of flower color in grasspea, with the responsible QTL located between 308.437 cM and 311.346 cM in LG4. The results can aid grasspea genome assembly and accelerate the selective breeding of new grasspea germplasm resources

Quantitative measurement of biofilm formation as indicated by absorbance at OD₅₉₀ in <i>Xv</i>.

<p>Quantitative measurement of biofilm formation as indicated by absorbance at OD₅₉₀ in <i>Xv</i>.</p

Quantitative comparison of siderophore production in <i>Xv</i> strains.

<p>Black diamond: wild-type strain <i>Xv</i>17; black square: <i>fur</i> mutation strain fur-m; and black triangle: <i>fur</i> complementation strain fur-c. </p

PCR primers used in this study.

<p>PCR primers used in this study.</p

Effect of <i>fur</i> in <i>Xv</i> virulence on tomato leaves.

<p>Fifty-day-old tomato plants (cv No.4 Zhongshu) were spray inoculated with A) <i>Xv</i>17; B) fur-m; C) fur-c; and D) LB medium (negative control).</p

Bacterial strains and plasmids used in this study.

<p>Bacterial strains and plasmids used in this study.</p

Comparison of siderophore production in <i>Xv</i> strains using the Chrome azurol S assay.

<p>Yellow halos around bacterial colonies indicate siderophore production. <i>Xv</i>17: wild-type <i>Xv</i> strain; fur-m: <i>fur</i> mutation strain of <i>Xv</i> 17; and fur-c: <i>fur</i> complementation strain of fur-m.</p