High doses of 2,4-D applied to sensitive dicots result in abnormal growth, premature senescence, and tissue decay ( Grossmann, 2010). At very low concentrations, 2,4-D mimics natural auxin in promoting cell division and elongation, while it exhibits herbicidal activity at high concentrations ( Grossmann, 2000 Song, 2014).
With the complex allotetraploid genomes of the two Gossypium species in hand and recombination and segregation data for genomic regions during the development of chromosome substitution lines, complementation of alleles leading to the identification of good recombinants can be a source of a novel gene for cotton genetic improvement on traits like herbicide tolerance ( Saha et al., 2006 Li et al., 2015 Zhang et al., 2015).Ģ,4-D is a popular synthetic auxin that kills unwanted dicot plants ( Schulz and Sehobye, 2016). In previous experiments, CS-B15sh exhibited reduced herbicide injury compared to TM-1 cotton seedlings when treated with 2,4-D at 1× field rate in greenhouse and field conditions ( Perez, 2021). Pima 379 via hybridization, cytogenetic analysis of progeny, and molecular marker selection ( Stelly et al., 2005 Saha et al., 2012). hirsutum L.) with introgressions on the short arm of chromosome 15 from G.
A chromosome substitution line CS-B15sh was developed in the genetic background of Texas Marker-1 or TM-1 ( G. is known to be sensitive to 2,4-dichlorophenoxyacetic acid (2,4-D), and understanding the genetics of herbicide tolerance and identification of specific gene(s) involved at the molecular level is crucial for the development and genetic improvement of herbicide-resistant commercial cotton. barbadense is superior in fiber quality, producing extra-long fibers for superior textile products ( Saha et al., 2006 Li et al., 2015 Liu et al., 2015).
hirsutum accounts for more than 90% of Upland cotton production worldwide, G. Gossypium hirsutum and Gossypium barbadense are two cultivated species of allotetraploid cotton. Gene set enrichment analysis on the union DEGs of the three cotton genotypes revealed the depletion of transcripts involved in photosynthesis and enrichment of transcripts involved in ABA response and signaling. It is interesting to note that glutathione S-transferase was differentially expressed in both CS-B15sh and Pima 379 but not in TM-1, while cytochrome P450 and other genes involved in the oxidation–reduction process were significantly expressed only in CS-B15sh in response to 2,4-D. Some genes associated with herbicide metabolism, including flavin monooxygenase (Gohir.A01G174100) and FAD-linked oxidase (Gohir.D06G002600), exhibited at least a twofold increase in CS-B15sh than in TM-1 (the gene was not expressed in Pima 379), suggesting a potential relationship between the gene’s expression and 2,4-D tolerance. Several components of the 2,4-D/auxin-response pathway-including ubiquitin E3 ligase, PB1|AUX/IAA, ARF transcription factors, and F-box proteins of the SCF TIR1/AFB complex-were upregulated with at least threefold higher expression in TM-1 compared with CS-B15sh, while both Pima 379 and TM-1 showed the same fold change expression for PB1|AUX/IAA mRNA. Here, we used RNA sequencing (RNA-seq) to determine the differential expression of genes between 2,4-D-challenged and control plants of the tolerant (CS-B15sh) and susceptible lines (TM-1 and Pima 379). Our results indicate a potential 2,4-D tolerance mechanism in CS-B15sh involving altered movement of 2,4-D. In a previous experiment, we observed reduced translocation of 2,4-D outside the treated leaf tissue in CS-B15sh, which contrasted with an increased translocation of the herbicide in the tissues above and below the treated leaf in TM-1. cv TM-1 and has chromosome introgression on the short arm of chromosome 15 from Gossypium barbadense L. CS-B15sh was developed in the genetic background of Gossypium hirsutum L. The cotton chromosome substitution line, CS-B15sh, exhibits 41% lower injury from 2,4-D when applied at the field recommended rate of 1.12 kg ae ha −1 (1×) than does Texas Marker-1 (TM-1).
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