Duarte-Delgado, Diana: Insights into the salt stress adaptation mechanisms of bread wheat genotypes using a systemic approach. - Bonn, 2020. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-59630
@phdthesis{handle:20.500.11811/8599,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-59630,
author = {{Diana Duarte-Delgado}},
title = {Insights into the salt stress adaptation mechanisms of bread wheat genotypes using a systemic approach},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2020,
month = sep,

note = {Bread wheat is one of the most important crops for the human diet but the increasing soil salinization is causing yield reductions worldwide. The development of appropriate cultivars requires the elucidation of mechanisms of tolerance to salt stress. To study them, physiological, genetic, transcriptomics and bioinformatics analyses were integrated. The dynamic transcriptomic response to salt stress was evaluated using the Massive Analysis of cDNA 3’-Ends (MACE) sequencing protocol in contrasting wheat genotypes from two mapping populations. The leaf transcriptome from Syn86 (salt-susceptible) and Zentos (salt-tolerant) was studied at the photosynthesis turning points identified at the osmotic phase. At the ionic phase, Bobur (salt-susceptible) and Altay2000 (salt-tolerant) were analyzed at 11 days and 24 days after stress exposure. Results revealed that genes involved in calcium-binding and cell wall synthesis were highly expressed in the tolerant genotype at the osmotic phase. On the other hand, the transcriptional suppression of photosynthesis-related and calcium-binding genes in the susceptible genotype was linked with the observed photosynthesis inhibition. At the ionic stage, more ABC transporters and Na+/Ca2+ exchangers were up-regulated in the tolerant genotype, indicating that mechanisms related to Na+ exclusion and transport may be vital for tissue tolerance at this phase. Moreover, genes involved in mechanisms related to protein synthesis and breakdown were identified at both osmotic and ionic phases. Based on the linkage disequilibrium blocks, the possible salt-responsive genes operating in pathways leading to salt stress tolerance were identified in the QTL intervals. These analyses provided systematic insights into the adaptation mechanisms of salt-tolerant and salt-sensitive wheat genotypes at both salt stress phases.
The over-represented calcium-binding category was analyzed with more detail at the expression and sequence level as the Ca2+ signaling events at the early stages of the osmotic phase are crucial for the acclimation response of the plants. Zentos showed primarily the up-regulation of genes at 15 minutes after stress whereas Syn86 displayed the down-regulation at 30 minutes. These results indicated that the distinct timing and the opposite transcriptional regulation of calcium-binding genes during the osmotic phase might represent key factors in the differential salt stress response. The RT-qPCR analysis of two of these genes has confirmed the differential expression in the contrasting genotypes. The comparative phylogenetic analysis revealed that genes that can be involved in the pathway for systemic Reactive Oxygen Species (ROS) production are different and are expressed in different time points in the genotypes studied. The identification of polymorphisms in promoter sequences and 3’-ends of genes provided insights on potential molecular mechanisms controlling the differential expression of these transcripts through differential transcription factor binding affinity or altered mRNA stability. The transcriptional divergences observed in the contrasting genotypes suggest a particular calcium signature in each genotype that can result in the activation or suppression of specific gene networks dependent on Ca2+ signaling. Therefore, these transcriptional events might be crucial in triggering either tolerance or susceptibility responses to salt stress in wheat.},

url = {http://hdl.handle.net/20.500.11811/8599}
}

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