Search

Secondary plant metabolites such as polyphenols and flavonols play an important role in plant defense and host–pathogen interaction. In this study, metabolomics and quantitative gene expression analysis was used to identify the polyphenols and flavonols, and the genes involved in resistance to clubroot disease in Brassica napus. For this, a set of clubroot susceptible and resistant canola lines, carrying resistance of the rutabaga cv. Polycross was inoculated with a virulent Plasmodiophora brassicae pathotype 3A to examine disease progression at 7-, 14- and 21 days after inoculation (DAI). The root samples collected at these time points were used for metabolomics and quantitative gene expression analyses. An increased concentration of several metabolites such as caffeic acid, protocatechuic aldehyde, vanillin and kaempferol, derived from phenylpropanoid and flavonoid biosynthesis pathways, were observed in roots of the resistant lines in response to P. brassicae infection implying that they might play a role in clubroot resistance. The higher expression of the genes C4H-A, C4H-B, CCR, CHI, CHS and F3H involved in the biosynthesis of these compounds substantiated the metabolomics analysis results. Conversely, significantly greater contents of ferulic acid and 3,4-hydroxybenzoic acid were found in roots of the susceptible lines indicating their possible role in disease susceptibility. Thus, the results from this study provide an insight into Brassica-P. brassicae interaction and the molecular basis of clubroot resistance. [ABSTRACT FROM AUTHOR]

Rutabaga (Brassica napus var. napobrassica) carries alleles that can broaden the genetic base of the spring canola. QTL analysis was performed by using a doubled haploid and a pedigree population of rutabaga × spring canola to identify the genomic regions of rutabaga controlling clubroot resistance, vernalization requirement and days-to-flowering and seed oil, protein, erucic acid and glucosinolate contents. Two QTL from chromosomes A8 and A3 were identified for resistance to clubroot disease where rutabaga alleles conferred resistance. A major QTL for vernalization response in rutabaga was mapped on A2 and this genomic region also affected days-to-flowering in spring growth habit plants. An additional QTL for days-to-flowering was detected on C6. A QTL for seed oil content was detected on C3 where rutabaga allele increased 0.7% oil. A protein QTL exerting an opposite effect was also detected in this genomic region, and an erucic acid QTL was detected about 16 cM away from the oil QTL. A major QTL for seed glucosinolate content was detected on A9. Clubroot resistance of rutabaga did not exert any effect on the flowering or seed quality traits. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are a class of small endogenous RNAs conserved in eukaryotic organisms including plants. They suppress gene expression posttranscriptionally in many different biological processes. Previously, we reported salinity-induced changes in gene expression in transgenic Arabidopsis thaliana plants that constitutively expressed a pea abscisic acid-responsive ( ABR17) gene. In the current study, we used microarrays to investigate the role of miRNA-mediated posttranscriptional gene regulation in these same transgenic plants in the presence and absence of salinity stress. We identified nine miRNAs that were significantly modulated due to ABR17 gene expression and seven miRNAs that were modulated in response to salt stress. The target genes regulated by these miRNAs were identified using sRNA target Base (starBase) degradome analysis and through 5′-RNA ligase-mediated rapid amplification of cDNA ends (RLM-RACE). Our findings revealed miRNA-mRNA interactions comprising regulatory networks of auxin response factor (ARF), argonaute 1 (AGO1), dicer-like proteins 1 (DCL1), SQUAMOSA promoter binding (SPB), NAC, APETALA 2 (AP2), nuclear factor Y (NFY), RNA-binding proteins, A. thaliana vacuolar phyrophosphate 1 (AVP1), and pentatricopeptide repeat (PPR) in ABR17-transgenic A. thaliana, which control physiological, biochemical, and stress signaling cascades due to the imposition of salt stress. Our results are discussed within the context of the effect of the transgene, ABR17, and the roles of miRNA expression may play in mediating plant responses to salinity. [ABSTRACT FROM AUTHOR]