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Molecular aspects of the role of root hairs during water stress in barley

ABSTRACT: The important parts of the root system are root hairs, which play a role in mineral and water uptake. Here, we present an analysis of the transcriptomic response to water deficiency of the wild-type (WT) barley cultivar ‘Karat’ and its root hairless mutant rhl1.a. A comparison of the transcriptional changes induced by water stress resulted in the identification of genes whose expression was specifically affected in each genotype. At the onset of water stress, more genes were modulated by water shortage in the roots of the WT plants than in the roots of the rhl1.a. The roots of the WT plants, but not of the rhl1.a, specifically responded with the induction of genes that are related to the ABA biosynthesis, stomata closure and cell wall biogenesis, thus indicating the specific activation of processes that are related to water stress signalling and protection. On the other hand, the processes of further response to abiotic stimuli, including hydrogen peroxide, heat and high light intensity, were specifically up-regulated in the leaves of the rhl1.a. An extended period of severe stress caused more drastic transcriptome changes in the roots and leaves of the rhl1.a mutant than in those of the WT. These results are in agreement with the much stronger damage to photosystem II in the rhl1.a mutant than in its parent cultivar after ten days of water stress. Taking into account the putative stress sensing and signalling features of the root hair transcriptome, we discuss the role of root hairs as sensors of environmental conditions.

ORGANISM(S): Hordeum vulgare

PROVIDER: GSE73789 | GEO | 2015/10/08

SECONDARY ACCESSION(S): PRJNA297975

REPOSITORIES: GEO

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Project description:Azospirillum is a plant growth promoting rhizobacteria (PGPR) with ability to produce several phytohormones such as auxins, mainly indole-3-acetic acid (IAA). The positive interaction of Azospirillum with plants has been simplified and explained through the bacterial capacity to produce IAA. Typical changes on root architecture by promoting the number of lateral roots and hair formation, and reducing the primary root length were established in inoculated plants. These changes increase the root surface improving the water and nutrients acquisition, and thus the growth of the whole plant. The mechanisms by which Azospirillum induces such changes fails to be explained only by the bacterial capacity to produce IAA. In this work, we have evaluated the root architecture and gene expression changes occurred in Arabidopsis thaliana inoculated with A. brasilense Az39 and the IAA-deficient mutant (Az39 ipdC-), or treated with exogenous IAA solution to confirm both, the IAA-dependent and IAA-independent Azospirillum´s pathways to promote the root growth. Our results demonstrate the ability of Az39 to modify the primary root development through IAA biosynthesis, while other IAA-independent mechanisms were related to an increase in the lateral roots development and the root hairs number. Jasmonates, ethylene and salicylic acid were increased in the IAA-deficient bacterial treatments, as the ipdC mutant significantly up-regulated transcription of genes enriched of these phytohormones signaling after 7 days. Further, the physical presence of the inactive bacteria (Az39φ) seems to mediate the development of root hairs, a mechanism common to other non-PGPR as E. coli DH5α. Our results suggest that Az39 inoculation induces morphological changes in root architecture through both IAA-dependent and independent mechanism. The IAA biosynthesis by Az39 reduces the primary root length; while the cells contact with the roots increases the root hairs production. Both the synthesis of active IAA and the presence of metabolically active Az39 cells increase the growth and development of lateral roots.

Project description:Global gene expression was compared between roots of cotton plants (variety Sicot 71) flooded for 4 hours and roots of unflooded cotton plants. Global gene expression was also compared between leaves of cotton plants (variety Sicot 71) flooded for 24 hours and leaves of unflooded cotton plants. Waterlogging stress causes yield reductions in cotton (Gossypium hirsutum L.). A major component of waterlogging stress is the lack of oxygen available to submerged tissues. While changes in expressed protein, gene transcription and metabolite levels have been studied in response to low oxygen stress, little research has been done on molecular responses to waterlogging in cotton. We assessed cotton growth responses to waterlogging and assayed global gene transcription responses in root and leaf cotton tissues of partially submerged plants. Waterlogging causes significant reductions in stem elongation, shoot mass, root mass, and leaf number. At the global gene expression level waterlogging significantly alters the expression of 1012 genes (4.2% of genes assayed) in root tissue as early as 4h after flooding. Many of these genes are associated with cell wall modification and growth pathways, glycolysis, fermentation, mitochondrial electron transport and nitrogen metabolism. Waterlogging of plant roots also altered global leaf gene expression, significantly changing the expression of 1305 genes (5.4% of genes assayed) after 24h of flooding. Genes associated with cell wall growth and modification, tetrapyrrole synthesis, hormone response, starch metabolism and nitrogen metabolism were affected in leaf tissues of waterlogged plants. Implications of these results for the development of waterlogging tolerant cotton are discussed. Keywords: Stress Response Plants of cotton cultivar Sicot 71 were grown to the two-leaf stage in tubs. For stress treatments plants were either watered as normal or flooded with water to completely submerge the root system. At four and twenty-four hours post-flooding samples of root or leaf tissue were taken from control and flooded plants. Total RNA was extracted from each tissue sample and assayed on cotton Affymetrix chips. Two biological replications were used for each comparison.

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Molecular aspects of the role of root hairs during water stress in barley

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