Project description:Pollen development is central for plant reproduction and is assisted by changes of the transcriptome and the proteome. At the same time, pollen is largely heat sensitive, particularly at early developmental stages. To define the changes during development and the response of different stages to elevated temperatures we investigated the transcriptome and proteome of pollen at tetrad, post-meiotic and mature stage before and after application of elevated temperatures. We used Solanum lycopersicum as an economically important crop. We demonstrate that the number of transcripts declines from tetrad to mature stage, while the protein content shows the opposite trend. Comparison of the transcriptome and proteome led to the discovery of two translational modes assigned as direct translation – transcripts increased in a specific pollen stage lead to increased translation in the same stage – and delayed translation – transcripts are produced for translation in later stages. The response to elevated temperatures is with ~5% of all genes being upregulated comparable to general plant behavior. The alteration at proteome level marked the mature pollen as least responsive and the post-meiotic stages as most responsive with altered levels of 40% of the identified proteins. For a subset of the genes with direct translation we observed a downregulation of protein levels after heat stress, whereas some of the genes with delayed translation showed a shift from delayed to direct translation when heat stress is applied. Further, Hsps, proteasome subunits, ribosomal proteins as well as eukaryotic initiation factors are the most drastically affected groups. On the example of Hsps we document that the response at transcriptome and proteome levels in e.g. the post-meiotic and mature stage does not correlate. Moreover, while all stages respond to heat stress with regulation of transcript abundance of Hsps in a comparable manner, changes at proteome level are distinct. Thus, we demonstrate that the difference in heat stress response in different stages of pollen development is rather manifested by significant changes of protein than transcript abundance. ------------------------------------------------------- Solanaceae Pollen Thermotolerance Initial Training Network (SPOT-ITN) Consortium

Project description:Pollen development is central for plant reproduction and is assisted by changes of the transcriptome and the proteome. At the same time, pollen is largely heat sensitive, particularly at early developmental stages. To define the changes during development and the response of different stages to elevated temperatures we investigated the transcriptome and proteome of pollen at tetrad, post-meiotic and mature stage before and after application of elevated temperatures. We used Solanum lycopersicum as an economically important crop. We demonstrate that the number of transcripts declines from tetrad to mature stage, while the protein content shows the opposite trend. Comparison of the transcriptome and proteome led to the discovery of two translational modes assigned as direct translation – transcripts increased in a specific pollen stage lead to increased translation in the same stage – and delayed translation – transcripts are produced for translation in later stages. The response to elevated temperatures is with ~5% of all genes being upregulated comparable to general plant behavior. The alteration at proteome level marked the mature pollen as least responsive and the post-meiotic stages as most responsive with altered levels of 40% of the identified proteins. For a subset of the genes with direct translation we observed a downregulation of protein levels after heat stress, whereas some of the genes with delayed translation showed a shift from delayed to direct translation when heat stress is applied. Further, Hsps, proteasome subunits, ribosomal proteins as well as eukaryotic initiation factors are the most drastically affected groups. On the example of Hsps we document that the response at transcriptome and proteome levels in e.g. the post-meiotic and mature stage does not correlate. Moreover, while all stages respond to heat stress with regulation of transcript abundance of Hsps in a comparable manner, changes at proteome level are distinct. Thus, we demonstrate that the difference in heat stress response in different stages of pollen development is rather manifested by significant changes of protein than transcript abundance.

Project description:Climate change is causing temperature increment in crop production areas worldwide, generating conditions of heat stress that negatively affect crop productivity. Tomato (Solanum lycopersicum), a major vegetable crop, is highly susceptible to conditions of heat stress. When tomato plants are exposed to ambient day/night temperatures that exceed 32 °C/20 °C, respectively, during the reproductive phase, fruit set and fruit weight are reduced, leading to a significant decrease in yield. Processing tomato cultivars are cultivated in open fields, where environmental conditions are not controlled; therefore, plants are exposed to multiple abiotic stresses, including heat stress. Nonetheless, information on stress response in processing tomatoes is very limited. Understanding the physiological response of modern processing tomato cultivars to heat stress may facilitate the development of thermotolerant cultivars. Here, we compared two tomato processing cultivars, H4107 and H9780, that we found to be constantly differing in yield performance. Using field and temperature-controlled greenhouse experiments, we show that the observed difference in yield is attributed to the occurrence of heat stress conditions. In addition, fruit set and seed production were significantly higher in the thermotolerant cultivar H4107, compared with H9780. Despite the general acceptance of pollen viability as a measure of thermotolerance, there was no difference in the percentage of viable pollen between H4107 and H9780 under either of the conditions tested. In addition to observations of similar pollen germination and bud abscission rates, our results suggest that processing tomato cultivars may present a particular case, in which pollen performance is not determining reproductive thermotolerance. Our results also demonstrate the value of combining controlled and uncontrolled experimental settings, in order to validate and identify heat stress-related responses, thus facilitating the development of thermotolerant processing tomato cultivars.

Project description:Heat stress is a major cause for yield loss in many crops, including vegetable crops. Even short waves of high temperature, becoming more frequent during recent years, can be detrimental. Pollen development is most heat-sensitive, being the main cause for reduced productivity under heat-stress across a wide range of crops. The molecular mechanisms involved in pollen heat-stress response and thermotolerance are however, not fully understood. Recently, we have demonstrated that ethylene, a gaseous plant hormone, plays a role in tomato (Solanum lycopersicum) pollen thermotolerance. These results were substantiated in the current work showing that increasing ethylene levels by using an ethylene-releasing substance, ethephon, prior to heat-stress exposure, increased pollen quality. A proteomic approach was undertaken, to unravel the mechanisms underlying pollen heat-stress response and ethylene-mediated pollen thermotolerance in developing pollen grains. Proteins were extracted and analyzed by means of a gel LC-MS fractionation protocol, and a total of 1,355 proteins were identified. A dataset of 721 proteins, detected in three biological replicates of at least one of the applied treatments, was used for all analyses. Quantitative analysis was performed based on peptide count. The analysis revealed that heat-stress affected the developmental program of pollen, including protein homeostasis (components of the translational and degradation machinery), carbohydrate, and energy metabolism. Ethephon-pre-treatment shifted the heat-stressed pollen proteome closer to the proteome under non-stressful conditions, namely, by showing higher abundance of proteins involved in protein synthesis, degradation, tricarboxylic acid cycle, and RNA regulation. Furthermore, up-regulation of protective mechanisms against oxidative stress was observed following ethephon-treatment (including higher abundance of glutathione-disulfide reductase, glutaredoxin, and protein disulfide isomerase). Taken together, the findings identified systemic and fundamental components of pollen thermotolerance, and serve as a valuable quantitative protein database for further research.

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Untargeted metabolomic analysis of tomato pollen development and heat stress response.

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Untargeted metabolomic analysis of tomato pollen development and heat stress response.

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