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Heat shock response of til1-1 mutant plants

ABSTRACT: Several lipocalin genes from higher plants were shown to be responsive to both high and low temperature stresses and have been named as temperature-induced lipocalin (Til). In this study, a reverse genetic approach was taken to elucidate the role of Arabidopsis Til1 (At5g58070) in thermotolerance. We showed that Til1 proteins was constitutively expressed and increased significantly after heat shock treatment. A T-DNA knockout line of Til1, designated as til1-1, could not produce Til1 and showed severe defects in basal and acquired thermotolerance. Introducing a wild type copy of Til1 gene into til1-1 complemented the mutant phenotype. Over-expression of Til1 in the wild type plant did not enhance thermotolerance. Til1 is peripherally associated with plasma membrane, suggesting a regulatory or protective role of this protein in membrane function. Transcriptomic analysis showed that the heat shock response in til1-1 was not altered as compared to the wild type plants. The temperature threshold for heat shock protein induction was not affected by the level of Til1. Ion leakage analysis revealed no significant difference in membrane stability between the wild type and til1-1 seedlings. These results suggested that Til1 is not involved in regulating membrane fluidity or stability. Nevertheless, the level of malondialdehyde was significantly higher in til1-1 than in the wild type after severe heat treatment. The mutant plants were also more sensitive than the wild type to tert-butyl hydroperoxide, a reagent that induces lipid peroxidation. Taken together, our data indicate that Til1 is an essential component for thermotolerance probably by acting against lipid peroxidation induced by severe heat stress.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE12619 | GEO | 2009/08/28

SECONDARY ACCESSION(S): PRJNA113083

REPOSITORIES: GEO

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Project description:Several lipocalin genes from higher plants were shown to be responsive to both high and low temperature stresses and have been named as temperature-induced lipocalin (Til). In this study, a reverse genetic approach was taken to elucidate the role of Arabidopsis Til1 (At5g58070) in thermotolerance. We showed that Til1 proteins was constitutively expressed and increased significantly after heat shock treatment. A T-DNA knockout line of Til1, designated as til1-1, could not produce Til1 and showed severe defects in basal and acquired thermotolerance. Introducing a wild type copy of Til1 gene into til1-1 complemented the mutant phenotype. Over-expression of Til1 in the wild type plant did not enhance thermotolerance. Til1 is peripherally associated with plasma membrane, suggesting a regulatory or protective role of this protein in membrane function. Transcriptomic analysis showed that the heat shock response in til1-1 was not altered as compared to the wild type plants. The temperature threshold for heat shock protein induction was not affected by the level of Til1. Ion leakage analysis revealed no significant difference in membrane stability between the wild type and til1-1 seedlings. These results suggested that Til1 is not involved in regulating membrane fluidity or stability. Nevertheless, the level of malondialdehyde was significantly higher in til1-1 than in the wild type after severe heat treatment. The mutant plants were also more sensitive than the wild type to tert-butyl hydroperoxide, a reagent that induces lipid peroxidation. Taken together, our data indicate that Til1 is an essential component for thermotolerance probably by acting against lipid peroxidation induced by severe heat stress. Experiment Overall Design: Total RNA was isolated from the seedlings of 7-d old wild-type and til1-1 mutant seedlings (a pool of about 100 plants per treatment in duplicates) harvested immediately after heat shock treatment. In this experiment, total 8 chips were used, 1 each for 2 biological replicates of the control and HS-treated samples for the wild type and mutant plants.

Project description:Analysis of transcriptome in moss Physcomitrella patens CNGCb null mutant at 25 and 34 degrees C for 30 minutes. Results provide insight into role of CNGCb in acquired thermotolerance induced by non-lethal heat treatment. Typically at dawn of a hot summer day, land plants need precise molecular thermometers to sense harmless increments in the ambient temperature to timely develop a heat-shock response (HSR) and accumulate protective heat shock proteins (Hsps), in anticipation of upcoming harmful temperatures at mid-day. Here, we found that the CNGCb gene from Physcomitrella patens and its Arabidopsis ortholog CNGC2, encode for a component of cyclic nucleotide gated Ca2+ channels acting as the primary thermosensors of land plant cells. Disruption of CNGCb or CNGC2 produced a hyper-thermosensitive phenotype, giving rise to a HSR and acquired thermotolerance at significantly milder heat-priming treatments than in wild type plants. In an aequorin-expressing moss, CNGCb loss-of-function caused altered Ca2+ signaling and a sustained Ca2+ influx. Patch clamp recordings on moss protoplasts showed the presence of three distinct thermo-responsive Ca2+-channels in wild type cells. Deletion of CNGCb led to a total absence of one, and it increased the open probability of the remaining two thermo-responsive Ca2+ channels. Thus, both in Arabidopsis and moss, CNGC2 and CNGCb are expected to form with other related CNGCs, heteromeric Ca2+ channels in the plasma membrane that respond to mild increments in the ambient temperature by triggering an optimal HSR, leading to the onset of plant acquired thermotolerance. The WT moss tissues were heat-shocked for a half an hour at 34°C and 38°C and CNGCb at 25and 34°C followed by liquid nitrogen freezing. Total RNA was isolated using RNeasy Mini Kit (QIAGEN, Hilden, Germany) and two biological replicate samples for each treatment, were extracted. An Agilent-certified microarray service lab (MOgene, LC, St. Louis, MO, USA) was used to verify the integrity of the RNA and perform the microarray experiments. Two biological replicates were performed.

Project description:The expression of heat-shock proteins (Hsps) induced by a non-lethal heat treatment confers acquired thermotolerance (AT) to organisms against a subsequent challenge of otherwise lethal temperature. After stress signal lifted, AT gradually decayed with the decline of Hsps during recovery period. The duration of AT may be critical for sessile organisms, such as plants, to survive repeated heat stress in the environment. To identify heat-induced genes involved in duration of AT, we took a reverse-genetics approach by screening for Arabidopsis T-DNA insertion mutants that show decreased thermotolerance after a long recovery at non-stress condition following a conditioning treatment. Among the tested mutants corresponding to 47 genes, only the HsfA2 knockout mutant showed significant phenotype. The mutant plants were more sensitive to severe heat stress than the wild type after long but not short recovery following a pretreatment at 37oC, which can be complemented by introducing a wild-type copy of the gene. Quantitative hypocotyl elongation assay also revealed that AT decayed faster in the absence of HsfA2. Significant decline of the transcript levels of several highly heat-induced genes was observed in the HsfA2 knockout plants after a 4-h recovery or after 2 h of prolonged heat stress. Immunoblot anlysis showed that Hsa32 and class I small Hsp were lower in the mutant than in the wild type after a long recovery. Our results suggest that HsfA2 as a heat-induced transactivator sustains the post-stress expression of Hsp genes and extends the duration of AT in Arabidopsis. Experiment Overall Design: Total RNA was isolated from the seedlings of 5-d old wild-type and HsfA2 knockout mutant seedlings (a pool of about 100 plants per treatment in duplicates) harvested immediately after heat shock treatment. In this experiment, total 12 chips were used, 1 each for 2 biological replicates of the control and HS-treated samples for the wild type and mutant plants.

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Heat shock response of til1-1 mutant plants

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