Plant Thermotolerance Research Articles

The OsERF115/AP2EREBP110 Transcription Factor Is Involved in the Multiple Stress Tolerance to Heat and Drought in Rice Plants.

The AP2/EREBP family transcription factors play important roles in a wide range of stress tolerance and hormone signaling. In this study, a heat-inducible rice ERF gene was isolated and functionally characterized. The OsERF115/AP2EREBP110 was categorized to Group-IIIc of the rice AP2/EREBP family and strongly induced by heat and drought treatment. The OsERF115/AP2EREBP110 protein targeted to nuclei and suppressed the ABA-induced transcriptional activation of Rab16A promoter in rice protoplasts. Overexpression of OsERF115/AP2EREBP110 enhanced thermotolerance of seeds and vegetative growth stage plants. The OsERF115/AP2EREBP110 overexpressing (OE) plants exhibited higher proline level and increased expression of a proline biosynthesis P5CS1 gene. Phenotyping of water use dynamics of the individual plant indicates that the OsERF115/AP2EREBP110-OE plant exhibited better water saving traits under heat and drought combined stress. Our combined results suggest the potential use of OsERF115/AP2EREBP110 as a candidate gene for genetic engineering approaches to develop heat and drought stress-tolerant crops.

Genome-Wide Identification and Characterization of Hsf and Hsp Gene Families and Gene Expression Analysis under Heat Stress in Eggplant (Solanum melongema L.)

Under high temperature stress, a large number of proteins in plant cells will be denatured and inactivated. Meanwhile Hsfs and Hsps will be quickly induced to remove denatured proteins, so as to avoid programmed cell death, thus enhancing the thermotolerance of plants. Here, a comprehensive identification and analysis of the Hsf and Hsp gene families in eggplant under heat stress was performed. A total of 24 Hsf-like genes and 117 Hsp-like genes were identified from the eggplant genome using the interolog from Arabidopsis. The gene structure and motif composition of Hsf and Hsp genes were relatively conserved in each subfamily in eggplant. RNA-seq data and qRT-PCR analysis showed that the expressions of most eggplant Hsf and Hsp genes were increased upon exposure to heat stress, especially in thermotolerant line. The comprehensive analysis indicated that different sets of SmHsps genes were involved downstream of particular SmHsfs genes. These results provided a basis for revealing the roles of SmHsps and SmHsp for thermotolerance in eggplant, which may potentially be useful for understanding the thermotolerance mechanism involving SmHsps and SmHsp in eggplant.

Nitric oxide induced thermotolerance in strawberry plants by activation of antioxidant systems and transcriptional regulation of heat shock proteins

ABSTRACT An experiment was conducted to examine whether application of sodium nitroprusside (SNP), a donor of NO, can improve thermo-tolerance of strawberry (Fragaria × ananassa) plants through inducing antioxidant system, and up-regulating heat stress transcription factors (HSFs) and heat shock proteins (HSPs) genes. Ventana strawberry plants were exposed to various temperatures (25, 35, and 40°C) for 24 h after pre-treatment with 0, 50, and 100 μM SNP. Heat stress significantly induced malondialdehyde and hydrogen peroxide (H2O2) contents, and increased accumulation of proline, whereas reduced relative water content (RWC), leaf chlorophyll fluorescence, and carotenoid content. In addition, heat stress enhanced superoxide dismutase and guaiacol peroxidase activities, increased glutathione and ascorbic acid contents, and reduced catalase and ascorbate peroxidase activities. Pre-treatment with SNP, especially at 100 μM, ameliorated heat injury by controlling the overaccumulation of H2O2, reducing lipid peroxidation, improvement of RWC, and increasing the enzymatic and non-enzymatic antioxidants. Transcriptomic profiling analysis showed that the expression of FaTHSFA2a, FaTHSFB1a, HSP70, and HSP90 in SNP pre-treated plants was significantly higher than non-treated plants after 2 h of heat stress at 40°C. These results suggested that NO alleviates heat-induced oxidative damage by modulating antioxidant pathways and fast inducing the expression of heat-stress related genes.

The protein kinase CPK28 phosphorylates ascorbate peroxidase and enhances thermotolerance in tomato.

High temperatures are a major threat to plant growth and development, leading to yield losses in crops. Calcium-dependent protein kinases (CPKs) act as critical components of Ca2+ sensing in plants that transduce rapid stress-induced responses to multiple environmental stimuli. However, the role of CPKs in plant thermotolerance and their mechanisms of action remain poorly understood. To address this issue, tomato (Solanum lycopersicum) cpk28 mutants were generated using a CRISPR-Cas9 gene-editing approach. The responses of mutant and wild-type plants to normal (25°C) and high temperatures (45°C) were documented. Thermotolerance was significantly decreased in the cpk28 mutants, which showed increased heat stress-induced accumulation of reactive oxygen species (ROS) and levels of protein oxidation, together with decreased activities of ascorbate peroxidase (APX) and other antioxidant enzymes. The redox status of ascorbate and glutathione were also modified. Using a yeast two-hybrid library screen and protein interaction assays, we provide evidence that CPK28 directly interacts with cytosolic APX2. Mutations in APX2 rendered plants more sensitive to high temperatures, whereas the addition of exogenous reduced ascorbate (AsA) rescued the thermotolerance phenotype of the cpk28 mutants. Moreover, protein phosphorylation analysis demonstrated that CPK28 phosphorylates the APX2 protein at Thr-59 and Thr-164. This process is suggested to be responsive to Ca2+ stimuli and may be required for CPK28-mediated thermotolerance. Taken together, these results demonstrate that CPK28 targets APX2, thus improving thermotolerance. This study suggests that CPK28 is an attractive target for the development of improved crop cultivars that are better adapted to heat stress in a changing climate.

The calcium‐dependent protein kinase ZmCDPK7 functions in heat‐stress tolerance in maize

Global warming poses a serious threat to crops. Calcium-dependent protein kinases (CDPKs)/CPKs play vital roles in plant stress responses, but their exact roles in plant thermotolerance remains elusive. Here, we explored the roles of heat-induced ZmCDPK7 in thermotolerance in maize. ZmCDPK7-overexpressing maize plants displayed higher thermotolerance, photosynthetic rates, and antioxidant enzyme activity but lower H2 O2 and malondialdehyde (MDA) contents than wild-type plants under heat stress. ZmCDPK7-knockdown plants displayed the opposite patterns. ZmCDPK7 is attached to the plasma membrane but can translocate to the cytosol under heat stress. ZmCDPK7 interacts with the small heat shock protein sHSP17.4, phosphorylates sHSP17.4 at Ser-44 and the respiratory burst oxidase homolog RBOHB at Ser-99, and upregulates their expression. Site-directed mutagenesis of sHSP17.4 to generate a Ser-44-Ala substitution reduced ZmCDPK7's enhancement of catalase activity but enhanced ZmCDPK7's suppression of MDA accumulation in heat-stressed maize protoplasts. sHSP17.4, ZmCDPK7, and RBOHB were less strongly upregulated in response to heat stress in the abscisic acid-deficient mutant vp5 versus the wild type. Pretreatment with an RBOH inhibitor suppressed sHSP17.4 and ZmCDPK7 expression. Therefore, abscisic acid-induced ZmCDPK7 functions both upstream and downstream of RBOH and participates in thermotolerance in maize by mediating the phosphorylation of sHSP17.4, which might be essential for its chaperone function.

MdHARBI1, a MdATG8i-interacting protein, plays a positive role in plant thermotolerance

Autophagy is a major degradation pathway in plants for maintaining cellular homeostasis in response to various environmental stressors. ATG8 is one of a series of autophagy-related (ATG) proteins and plays a central role in both bulk and selective autophagy. Previously, we characterized MdATG8i in apple and demonstrated that it has a positive role in apple stress resistance. Although many ATG8-interacting proteins have been found in Arabidopsis, no protein has been reported to interact with MdATG8 in apple. Here, we identified MdHARBI1 as a MdATG8i-interacting protein in apple, however, the functions of HARBI1-like proteins have not been explored in plants. Expression analysis of MdHARBI1 and pro-MdHARBI1-GUS staining of transgenic Arabidopsis exposed to high temperature demonstrated that MdHARBI1 was significantly induced by heat stress. Moreover, heat-treated MdHARBI1-trangenic tomato plants maintained higher autophagic activity, accumulated fewer ROS, and displayed stronger chlorophyll fluorescence than wild-type plants. Because these phenotypes were consistent with those displayed by MdATG8i-overexpressing apple plants under high temperature, we concluded that the MdATG8i-interacting protein MdHARBI1 plays a critical role in the basal thermotolerance of plants, mainly by influencing autophagy pathways.

Melatonin improves heat tolerance in Actinidia deliciosa via carotenoid biosynthesis and heat shock proteins expression.

The whole-genome molecular mechanisms of melatonin (MT)-mediated enhancement of thermotolerance in plants has rarely been studied. In this study, the genome-wide gene expression profiles of kiwifruit seedlings primed with MT and non-MT at 45°C were analyzed by RNA-Seq. A total of 3299 differentially expressed genes (DEGs) were screened between MT and non-MT treatment, in which carotenoid biosynthesis was one of the high-enrichment pathways revealed by Kyoto Encyclopedia of Genes and Genomes analysis. Further, qRT-PCR verified that MT significantly induced the upregulated expression of the carotenoid biosynthesis gene, which was consistent with the increase of carotenoid content. In addition, 10 heat shock proteins (HSPs) were identified to have a highly upregulated expression by MT. These findings provide a set of informative and fundamental data on the role of MT in heat resistance.

A novel R2R3-MYB transcription factor LlMYB305 from Lilium longiflorum plays a positive role in thermotolerance via activating heat-protective genes

The R2R3-MYB transcription factors (TFs) have been reported to play important roles in the development, metabolism, and response to abiotic stresses of plants; however, relative to the numerous studies on the involvement of R2R3-MYBs response to drought, salinity, and cold stress, the function of these TFs in heat stress remains largely unknown. Here, we isolated a novel R2R3-MYB, named LlMYB305, from lily (Lilium longiflorum), which was closely related to the AtMYB21 and AtMYB24 of Arabidopsis. The LlMYB305 was induced by high temperature and the protein was primarily located in the nucleus and had transactivation ability in yeast and plant cells. The conserved C-terminal motif of LlMYB305 contributed to its transactivation ability. Overexpression of LlMYB305 caused pronounced growth and fertility defects in transgenic Arabidopsis plants; simultaneously, thermotolerance of the transgenic plants was elevated. The increase in thermotolerance might be due to the up-regulated expression of the heat-protective genes after heat stress treatment, although the genes were not induced and even inhibited under normal conditions in the transgenic plants. Further analysis showed LlMYB305 might be an up-stream regulator of LlHSC70. L1MYB305 repressed the promoter activity of LlHSC70 under normal conditions, but activated the promoter activity under heat stress, which suggested that LlMYB305 might need to be activated by high temperature to take part in the thermotolerance. This study identified an R2R3-MYB member, LlMYB305, from lily, which might play a positive role in thermotolerance.

Root endophyte induced plant thermotolerance by constitutive chromatin modification at heat stress memory gene loci.

Global warming has become a critical challenge to food security, causing severe yield losses of major crops worldwide. Conventional and transgenic breeding strategies to enhance plant thermotolerance are laborious and expensive. Therefore, the use of beneficial microbes could be an alternative approach. Here, we report that the root endophyte Enterobacter sp. SA187 induces thermotolerance in wheat in the laboratory as well as in open‐field agriculture. To unravel the molecular mechanisms, we used Arabidopsis thaliana as model plant. SA187 reprogramed the Arabidopsis transcriptome via HSFA2‐dependent enhancement of H3K4me3 levels at heat stress memory gene loci. Unlike thermopriming, SA187‐induced thermotolerance is mediated by ethylene signaling via the transcription factor EIN3. In contrast to the transient chromatin modification by thermopriming, SA187 induces constitutive H3K4me3 modification of heat stress memory genes, generating robust thermotolerance in plants. Importantly, microbial community composition of wheat plants in open‐field agriculture is not influenced by SA187, indicating that beneficial microbes can be a powerful tool to enhance thermotolerance of crops in a sustainable manner.

Short- and long-term effects of surface fires on heat stress protein content in Scots pine needles

Plants can minimise the damaging effects of high temperatures through numerous protective mechanisms; however, it is largely unknown how these mechanisms respond to extreme temperatures associated with wildfire. We investigated the effect of experimental burning (EB) on the accumulation of stress heat shock proteins (Hsps), which are one of the factors of thermotolerance in plants, in the needles of Scots pine (Pinus sylvestris L.). Previous fire exposure led not only to short- and long-term changes in the content of stress proteins in needles but also to changes in the accumulation of these proteins in response to reheating. The content of Hsp 101, Hsp 70 and Hsp 17.6 in the needles increased on the second day after EB (short-term effect of fire). Three years after EB, the content of Hsps in the fire-exposed needles was lower compared with the control needles. When these needles were subjected to the heat stress test at 45°C, the content of Hsps increased, whereas the content of Hsps in control needles decreased. Our results suggest that Scots pine needles retain a fairly long-term ‘stress memory’, expressed through proteomic defence mechanisms, to wildfire heat-induced damage.

HSP70-3 Interacts with Phospholipase Dδ and Participates in Heat Stress Defense

Heat shock proteins (HSPs) function as molecular chaperones and are key components responsible for protein folding, assembly, translocation, and degradation under stress conditions. However, little is known about how HSPs stabilize proteins and membranes in response to different hormonal or environmental cues in plants. Here, we combined molecular, biochemical, and genetic approaches to elucidate the involvement of cytosolic HSP70-3 in plant stress responses and the interplay between HSP70-3 and plasma membrane (PM)-localized phospholipase Dδ (PLDδ) in Arabidopsis (Arabidopsis thaliana). Analysis using pull-down, coimmunoprecipitation, and bimolecular fluorescence complementation revealed that HSP70-3 specifically interacted with PLDδ. HSP70-3 bound to microtubules, such that it stabilized cortical microtubules upon heat stress. We also showed that heat shock induced recruitment of HSP70-3 to the PM, where HSP70-3 inhibited PLDδ activity to mediate microtubule reorganization, phospholipid metabolism, and plant thermotolerance, and this process depended on the HSP70-3-PLDδ interaction. Our results suggest a model whereby the interplay between HSP70-3 and PLDδ facilitates the re-establishment of cellular homeostasis during plant responses to external stresses and reveal a regulatory mechanism in regulating membrane lipid metabolism.

Two interacting ethylene response factors regulate heat stress response.

The ethylene response factor (ERF) transcription factors are integral components of environmental stress signaling cascades, regulating a wide variety of downstream genes related to stress responses and plant development. However, the mechanisms by which ERF genes regulate the heat stress response are not well understood. Here, we uncover the positive role of ethylene signaling, ERF95 and ERF97 in basal thermotolerance of Arabidopsis thaliana. We demonstrate that ethylene signaling-defective mutants exhibit compromised basal thermotolerance, whereas plants with constitutively activated ethylene response show enhanced basal thermotolerance. EIN3 physically binds to the promoters of ERF95 and ERF97. Ectopic constitutive expression of ERF95 or ERF97 increases the basal thermotolerance of plants. In contrast, erf95 erf96 erf97 erf98 quadruple mutants exhibit decreased basal thermotolerance. ERF95 and ERF97 genetically function downstream of EIN3. ERF95 can physically interact with ERF97, and this interaction is heat inducible. ERF95 and ERF97 regulate a common set of target genes, including known heat-responsive genes and directly bind to the promoter of HSFA2. Thus, our study reveals that the EIN3-ERF95/ERF97-HSFA2 transcriptional cascade may play an important role in the heat stress response, thereby establishing a connection between ethylene and its downstream regulation in basal thermotolerance of plants.

Antagonistic Regulation by CPN60A and CLPC1 of TRXL1 that Regulates MDH Activity Leading to Plant Disease Resistance and Thermotolerance

Global warming and emerging plant diseases challenge agricultural food/feed production. We identify mechanism(s) regulating both plant thermotolerance and disease resistance. Using virus-induced gene silencing (VIGS)-based genetic screening, we identify a thioredoxin-like 1 (TRXL1) gene involved in plant nonhost disease resistance and thermotolerance. TRXL1 is reduced, partly degraded via proteases and proteasome, and alters its chloroplast localization during heat stress. TRXL1 interacts with more than 400 proteins, including chaperonin CPN60A, caseinolytic protease (CLPC1), and NADP-dependent malate dehydrogenase (NADP-MDH). Chaperonin 60A (CPN60A) guards TRXL1 from degradation, whereas CLPC1 degrades TRXL1 during heat stress. TRXL1 regulates NADP-MDH activity, leading to an increase in malate level and inhibition of superoxide radical formation. We show that CPN60A and NADP-MDH positively regulate nonhost resistance, and CPN60A positively and CLPC1 negatively regulate thermotolerance. This study shows an antagonistic post-translational regulation of TRXL1 by CPN60A and CLPC1 and regulation of MDH by TRXL1, leading to plant disease resistance and thermotolerance.

High temperature triggered plant responses from whole plant to cellular level

Agronomic productivity is facing a drastic decline because of increasing temperatures, which is a global concern presently. Plants can sense such temperature changes and manifest their responses through morphological, anatomical, phenological, biochemical, physiological, and molecular changes enabling plants to adapt to the new environments. The dissection of such plant responses enables the researchers to develop markers utilized to produce improved thermotolerant plants. High-temperature effects vary with plant developmental stages and plant species and profoundly affect the reproductive success and plant species’ geographical distribution. Water relations, membrane stability, respiration, and photosynthesis are adversely affected while hormone and metabolite, both primary and secondary, levels are also modulated. Plants respond by heat shock protein and related protein expression, ROS generation, membrane stability maintenance, osmoprotectant accumulation, MAPK and CDPK cascade induction, antioxidant production, and chaperone signalling, ultimately leading to thermotolerance. A summary of such plant responses from the whole plant to cellular levels, including molecular mechanisms, is presented in this review to have a thorough understanding regarding plant thermotolerance.

Exogenous calcium mitigates heat stress effects in common bean: a coordinated impact of photoprotection of PSII, up-regulating antioxidants, and carbohydrate metabolism

Calcium (Ca2+) is involved in mediating anti-stress responses in plants through one or combination of biochemical processes. Thus, the major objective of present study was to assess the protective effect of exogenous Ca2+ (0, 2.5, 5.0, and 7.5 mM) on photosynthetic machinery of cv. Jaguar and SER-16 under heat stress (HS 25–45 °C for 48 h). The applied HS (45 °C) caused substantial reduction in net photosynthetic rate (Pn 73%), photosystem II quantum yield (ΦII 24%), linear electron flow (LEF 13%), and SPAD values (27%) with imbalancing of sugars metabolism and redox potential. At heat stress (40 °C), plants of both cultivars tried to acclimate by regulating leaf temperature through increased stomatal conductance (gs 36%), transpiration rate (E 60%) and by increase in non-photochemical quenching (NPQ 19%). In addition, Ca2+ pre-treatment protected the membrane from oxidative damage by up-regulating the enzymatic activities and down-regulation of malondialdehyde (MDA) accumulation and electrolyte leakage in plant leaf tissues. Pre-treatment with Ca2+ enhanced the accumulation of sugars (glucose, fructose, inositol, and raffinose) in both heat stressed bean plants (45 °C). In conclusion, cv. Jaguar had greater tolerance to HS than SER-16, which is associated with Ca2+-induced photo-protective effect on PSII, the balance between LEF and reactive oxygen species (ROS) generation with concomitant up-regulation of antioxidant enzymes, and increase in compatible solutes. Based on changes in physiological attributes, it is speculated that Ca2+ application might have mediated thermo-tolerance in plants via Ca2+-sensing and signaling pathway, which needs to be verified through molecular studies.

Plant Bio-regulators for Enhancing Grain Yield and Quality of Legumes: A Review

Plant bio-regulators (PBRs) are hormone-like natural or synthetic compounds that are able to increase the yields, alter growth patterns, nutritional qualities and provide resistance to various kinds of stresses (cold, heat, drought, insect, diseases, salinity) when applied at very low concentration to the plants. PBRs are known to enhance source-sink relationship and help in stimulating the photosyntheates thereby reduce flower drop, helps in fruit and seed development in better way ultimately improving the yield of the crops. Nowadays, abiotic stresses are major factors limiting crop productivity and sustainability throughout the globe. Bio-regulators application on crops induces long-term thermo tolerance (heat and cold) in plants as these can modulate plant responses to stresses at the cellular, tissue or organ level and hence are able to enhance the yield, quality and nutritional aspects of the food and forage legumes in the changing climatic scenario. Application of bio-regulators on crops is farmer friendly, convenient and effective approach for improving the productivity and quality of legume crops. The influence of some of the important plant bioregulators on growth, yield, quality and stress management in important food and forage legume crops are reviewed in this article.

HOS1 activates DNA repair systems to enhance plant thermotolerance.

Plants possess an astonishing capability of effectively adapting to a wide range of temperatures, ranging from freezing to near-boiling temperatures1,2. Yet, heat is a critical obstacle to plant survival. The deleterious effects of heat shock on cell function include misfolding of cellular proteins, disruption of cytoskeletons and membranes, and disordering of RNA metabolism and genome integrity3-5. Plants stimulate diverse heat shock response pathways in response to abrupt temperature increases. While it is known that stressful high temperatures disturb genome integrity by causing nucleotide modifications and strand breakages or impeding DNA repair6, it is largely unexplored how plants cope with heat-induced DNA damages. Here, we demonstrated that high expression of osmotically reponsive genes 1 (HOS1) induces thermotolerance by activating DNA repair components. Thermotolerance and DNA repair capacity were substantially reduced in HOS1-deficient mutants, in which thermal induction of genes encoding DNA repair systems, such as the DNA helicase RECQ2, was markedly decreased. Notably, HOS1 proteins were thermostabilized in a heat shock factor A1/heat shock protein 90 (HSP90)-dependent manner. Our data indicate that the thermoresponsive HSP90-HOS1-RECQ2 module contributes to sustaining genome integrity during the acquisition of thermotolerance, providing a distinct molecular link between DNA repair and thermotolerance.

CaHsfA1d Improves Plant Thermotolerance via Regulating the Expression of Stress- and Antioxidant-Related Genes

Heat shock transcription factor (Hsf) plays an important role in regulating plant thermotolerance. The function and regulatory mechanism of CaHsfA1d in heat stress tolerance of pepper have not been reported yet. In this study, phylogenetic tree and sequence analyses confirmed that CaHsfA1d is a class A Hsf. CaHsfA1d harbored transcriptional function and predicted the aromatic, hydrophobic, and acidic (AHA) motif mediated function of CaHsfA1d as a transcription activator. Subcellular localization assay showed that CaHsfA1d protein is localized in the nucleus. The CaHsfA1d was transcriptionally up-regulated at high temperatures and its expression in the thermotolerant pepper line R9 was more sensitive than that in thermosensitive pepper line B6. The function of CaHsfA1d under heat stress was characterized in CaHsfA1d-silenced pepper plants and CaHsfA1d-overexpression Arabidopsis plants. Silencing of the CaHsfA1d reduced the thermotolerance of the pepper, while CaHsfA1d-overexpression Arabidopsis plants exhibited an increased insensitivity to high temperatures. Moreover, the CaHsfA1d maintained the H2O2 dynamic balance under heat stress and increased the expression of Hsfs, Hsps (heat shock protein), and antioxidant gene AtGSTU5 (glutathione S-transferase class tau 5) in transgenic lines. Our findings clearly indicate that CaHsfA1d improved the plant thermotolerance via regulating the expression of stress- and antioxidant-related genes.

Natural antisense transcripts of MIR398 genes suppress microR398 processing and attenuate plant thermotolerance

MicroRNAs (miRNAs) and natural antisense transcripts (NATs) control many biological processes and have been broadly applied for genetic manipulation of eukaryotic gene expression. Still unclear, however, are whether and how NATs regulate miRNA production. Here, we report that the cis-NATs of MIR398 genes repress the processing of their pri-miRNAs. Through genome-wide analysis of RNA sequencing data, we identify cis-NATs of MIRNA genes in Arabidopsis and Brassica. In Arabidopsis, MIR398b and MIR398c are coexpressed in vascular tissues with their antisense genes NAT398b and NAT398c, respectively. Knock down of NAT398b and NAT398c promotes miR398 processing, resulting in stronger plant thermotolerance owing to silencing of miR398-targeted genes; in contrast, their overexpression activates NAT398b and NAT398c, causing poorer thermotolerance due to the upregulation of miR398-targeted genes. Unexpectedly, overexpression of MIR398b and MIR398c activates NAT398b and NAT398c. Taken together, these results suggest that NAT398b/c repress miR398 biogenesis and attenuate plant thermotolerance via a regulatory loop.

Transcriptomic analysis of the heat-stress response in Boechera depauperata and Arabidopsis reveals a distinct and unusual heat-stress response in Boechera

Global surface temperatures are expected to rise throughout the 21st century, and negatively impact plant growth and reproduction. Thus, it is imperative that we deepen our understanding of plant thermotolerance. The examination of native plant species that have evolved tolerance to high temperatures can provide crucial information on how plants can adapt to climate change. Boechera (Brassicaceae), a large genus that is native to North America, is highly thermotolerant, and can maintain photosynthetic activity at high temperatures. Here we report results of transcriptomic studies that seek to reveal possible thermotolerance mechanisms in B. depauperata (A.Nelson & P.B.Kenn.) Windham & Al-Shehbaz. Analysis of RNA-seq datasets from heat stressed B. depauperata and Arabidopsis thaliana (L.) Heynh. plants identified significant differences in how each of these species responds to identical heat stress conditions. The most highly upregulated heat-stress genes in A. thaliana includes the well-characterized heat-shock genes. In contrast, the Boechera heat-stress response is composed of: novel genes that lack orthologs in other genomes; genes coding for proteins of uncharacterized function; and genes coding for proteins associated with the unfolded protein and endoplasmic reticulum stress responses. In addition, genes that are protective of photosynthetic capacity are also differentially upregulated in B. depauperata.