Perspectives on deciphering mechanisms underlying plant heat stress response and thermotolerance

Global warming is a major threat for agriculture and food safety and in many cases the negative effects are already apparent. The current challenge of basic and applied plant science is to decipher the molecular mechanisms of heat stress response (HSR) and thermotolerance in detail and use this information to identify genotypes that will withstand unfavorable environmental conditions. Nowadays X-omics approaches complement the findings of previous targeted studies and highlight the complexity of HSR mechanisms giving information for so far unrecognized genes, proteins and metabolites as potential key players of thermotolerance. Even more, roles of epigenetic mechanisms and the involvement of small RNAs in thermotolerance are currently emerging and thus open new directions of yet unexplored areas of plant HSR. In parallel it is emerging that although the whole plant is vulnerable to heat, specific organs are particularly sensitive to elevated temperatures. This has redirected research from the vegetative to generative tissues. The sexual reproduction phase is considered as the most sensitive to heat and specifically pollen exhibits the highest sensitivity and frequently an elevation of the temperature just a few degrees above the optimum during pollen development can have detrimental effects for crop production. Compared to our knowledge on HSR of vegetative tissues, the information on pollen is still scarce. Nowadays, several techniques for high-throughput X-omics approaches provide major tools to explore the principles of pollen HSR and thermotolerance mechanisms in specific genotypes. The collection of such information will provide an excellent support for improvement of breeding programs to facilitate the development of tolerant cultivars. The review aims at describing the current knowledge of thermotolerance mechanisms and the technical advances which will foster new insights into this process

The protein translocation systems in plants - composition and variability on the example of Solanum lycopersicum

Background: Protein translocation across membranes is a central process in all cells. In the past decades the molecular composition of the translocation systems in the membranes of the endoplasmic reticulum, peroxisomes, mitochondria and chloroplasts have been established based on the analysis of model organisms. Today, these results have to be transferred to other plant species. We bioinformatically determined the inventory of putative translocation factors in tomato (Solanum lycopersicum) by orthologue search and domain architecture analyses. In addition, we investigated the diversity of such systems by comparing our findings to the model organisms Saccharomyces cerevisiae, Arabidopsis thaliana and 12 other plant species. Results: The literature search end up in a total of 130 translocation components in yeast and A. thaliana, which are either experimentally confirmed or homologous to experimentally confirmed factors. From our bioinformatic analysis (PGAP and OrthoMCL), we identified (co-)orthologues in plants, which in combination yielded 148 and 143 orthologues in A. thaliana and S. lycopersicum, respectively. Interestingly, we traced 82% overlap in findings from both approaches though we did not find any orthologues for 27% of the factors by either procedure. In turn, 29% of the factors displayed the presence of more than one (co-)orthologue in tomato. Moreover, our analysis revealed that the genomic composition of the translocation machineries in the bryophyte Physcomitrella patens resemble more to higher plants than to single celled green algae. The monocots (Z. mays and O. sativa) follow more or less a similar conservation pattern for encoding the translocon components. In contrast, a diverse pattern was observed in different eudicots. Conclusions: The orthologue search shows in most cases a clear conservation of components of the translocation pathways/machineries. Only the Get-dependent integration of tail-anchored proteins seems to be distinct. Further, the complexity of the translocation pathway in terms of existing orthologues seems to vary among plant species. This might be the consequence of palaeoploidisation during evolution in plants; lineage specific whole genome duplications in Arabidopsis thaliana and triplications in Solanum lycopersicum

Utjecaj NaCl na fermentaciju zrelih zelenih rajčica cv. Ailsa Braig u rasolu

The effect of osmotic strength on gene expression and activity of the major enzymes of fermentative metabolism of mature green tomato fruit (Solanum lycopersicum cv. Ailsa Craig) has been studied by exposing fruit to brine containing 0 (water), 5 and 10 % NaCl. The fruits were surface sterilized prior to treatment to prevent the growth of microbes naturally present on the skin of the fruit. Changes in fruit expression of fermentation genes and the activity of the respective enzymes as well as physicochemical quality characteristics (soluble solid content, titratable acidity, pH and firmness) were studied in both fruit and brine for 0.5, 1, 1.5, 2, 3, 7 and 14 days. Discrepancies in responses that resulted from the different salt concentrations were obtained at molecular and quality levels. The complex kinetics of solutes between the fruit and the surrounding solution due to osmotic potential has led to different responses of the tissue to fermentation. Tomato fruit showed cracking soon after storage in water; water-stored fruit had higher titratable acidity, lower soluble solid content, and higher induction of anaerobic metabolism as indicated by the expression or the activity of the fermentation enzymes compared to fruit stored in brine with 5 or 10 % NaCl. No cracking was observed in fruit stored in 5 (isotonic) or 10 % NaCl (hypertonic) brine, though in the latter, signs of dehydration were observed. The presence of salt in brine reduced the intensity of fermentative metabolism as indicated by the lower gene expression and enzyme activity. However, fruit stored in brine with 5 % NaCl survived longer than with 0 or 10 % NaCl. The presence of 5 % NaCl in brine caused mild changes of both the fermentative metabolism and the physicochemical characteristics and prevented fruit deterioration during storage.U radu je ispitan utjecaj osmoze na ekspresiju gena i aktivnost glavnih enzima koji sudjeluju u fermentaciji zrelih zelenih rajčica (Solanum lycopersicum cv. Ailsa Craig), i to uranjanjem plodova u vodu i rasol što sadržava 5 ili 10 % NaCl. Površina je plodova prije obrade sterilizirana da bi se spriječio rast mikroorganizama na pokožici ploda. Analizirani su plodovi rajčice i rasol tijekom 0,5; 1; 1,5; 2; 3; 7 i 14 dana skladištenja, te ispitani ovi parametri: promjena ekspresije gena i aktivnost enzima koji sudjeluju u fermentaciji, te fizikalno-kemijska svojstva plodova (udio topljivih tvari, titracijska kiselost, pH-vrijednost i čvrstoća). Utvrđene su razlike u dobivenim rezultatima, i to na molekularnoj razini te u kakvoći plodova. Zaključeno je da utjecaj fermentacije na tkivo ploda rajčice ovisi o složenoj kinetici prelaska otopljenih tvari iz plodova u otopinu zbog razlike osmotskih tlakova. Skladištenje u vodi uzrokovalo je pucanje plodova koji su imali veću titracijsku kiselost i manji udio topljivih tvari. Ekspresija gena i aktivnost enzima pokazali su da je došlo do povećanja anaerobnog metabolizma u tim plodovima, u usporedbi s onima skladištenim u rasolu. Skladištenje plodova u izotoničnoj otopini (5 % soli) nije uzrokovalo njihovo pucanje, a u hipertoničnoj (10 % soli) otopini nije došlo do pucanja već do dehidracije plodova. Dodatkom soli smanjen je intenzitet fermentacije, što je dovelo do manje ekspresije gena i aktivnosti enzima. Trajnost plodova skladištenih u izotoničnoj otopini bila je veća od onih skladištenih u vodi ili hipertoničnoj otopini. Manja koncentracija soli u otopini nije bitno utjecala na metabolizam fermentacije te kakvoću plodova, a spriječila je njihovo propadanje tijekom skladištenja

A plant-specific clade of serine/arginine-rich proteins regulates RNA splicing homeostasis and thermotolerance in tomato

Global warming poses a threat for crops, therefore, the identification of thermotolerance mechanisms is a priority. In plants, the core factors that regulate transcription under heat stress (HS) are well described and include several HS transcription factors (HSFs). Despite the relevance of alternative splicing in HS response and thermotolerance, the core regulators of HS-sensitive alternative splicing have not been identified. In tomato, alternative splicing of HSFA2 is important for acclimation to HS. Here, we show that several members of the serine/arginine-rich family of splicing factors (SRSFs) suppress HSFA2 intron splicing. Individual-nucleotide resolution UV cross-linking and immunoprecipitation (iCLIP) combined with RNA-Seq revealed that RS2Z35 and RS2Z36, which make up a plant-specific clade of SR proteins, not only regulate HSFA2 but approximately 50% of RNAs that undergo HS-sensitive alternative splicing, with preferential binding to purine-rich RNA motifs. Single and double CRISPR rs2z mutant lines show a dysregulation of splicing and exhibit lower basal and acquired thermotolerance compared to wild type plants. Our results suggest that RS2Z35 and RS2Z36 have a central role in mitigation of the negative effects of HS on RNA splicing homeostasis, and their emergence might have contributed to the increased capacity of plants to acclimate to high temperatures

An Epigenetic Alphabet of Crop Adaptation to Climate Change

Crop adaptation to climate change is in a part attributed to epigenetic mechanisms which are related to response to abiotic and biotic stresses. Although recent studies increased our knowledge on the nature of these mechanisms, epigenetics remains under-investigated and still poorly understood in many, especially non-model, plants, Epigenetic modifications are traditionally divided into two main groups, DNA methylation and histone modifications that lead to chromatin remodeling and the regulation of genome functioning. In this review, we outline the most recent and interesting findings on crop epigenetic responses to the environmental cues that are most relevant to climate change. In addition, we discuss a speculative point of view, in which we try to decipher the epigenetic alphabet that underlies crop adaptation mechanisms to climate change. The understanding of these mechanisms will pave the way to new strategies to design and implement the next generation of cultivars with a broad range of tolerance/resistance to stresses as well as balanced agronomic traits, with a limited loss of (epi)genetic variability.COST (European Cooperation in Science and Technology) [CA19125]; Ministry for Innovation and Technology in Hungary [TKP2021-EGA-20]; Ministry of Education, Science and Technological Development of the Republic of Serbia [451-03-9/2021-14/200032]; Science Fund of the Republic of Serbia through IDEAS project Creating climate smart sunflower for future challenges (SMARTSUN) [7732457]This article is based upon work from COST Action EPI-CATCH (CA19125), supported by COST (European Cooperation in Science and Technology), www.cost.eu.JD was also supported by the Thematic Excellence Programme (TKP2021-EGA-20) of the Ministry for Innovation and Technology in Hungary, within the framework of the Biotechnology thematic program of the University of Debrecen, and DM by activities of Center of Excellence for Innovations in Breeding of Climate-Resilient Crops-Climate Crops, Institute of Field and Vegetable Crops, Novi Sad, Serbia, as well as by Ministry of Education, Science and Technological Development of the Republic of Serbia, grant number: 451-03-9/2021-14/200032, and the Science Fund of the Republic of Serbia, through IDEAS project Creating climate smart sunflower for future challenges (SMARTSUN) grant number 7732457

Stress biology: Complexity and multifariousness in health and disease.

Preserving and regulating cellular homeostasis in the light of changing environmental conditions or developmental processes is of pivotal importance for single cellular and multicellular organisms alike. To counteract an imbalance in cellular homeostasis transcriptional programs evolved, called the heat shock response, unfolded protein response, and integrated stress response, that act cell-autonomously in most cells but in multicellular organisms are subjected to cell-nonautonomous regulation. These transcriptional programs downregulate the expression of most genes but increase the expression of heat shock genes, including genes encoding molecular chaperones and proteases, proteins involved in the repair of stress-induced damage to macromolecules and cellular structures. Sixty-one years after the discovery of the heat shock response by Ferruccio Ritossa, many aspects of stress biology are still enigmatic. Recent progress in the understanding of stress responses and molecular chaperones was reported at the 12th International Symposium on Heat Shock Proteins in Biology, Medicine and the Environment in the Old Town Alexandria, VA, USA from 28th to 31st of October 2023