Seed tolerance to deterioration in arabidopsis is affected by virus infection

[EN] Seed longevity is the period during which the plant seed is able to germinate. This property is strongly influenced by environment conditions experienced by seeds during their formation and storage. In the present study we have analyzed how the biotic stress derived from the infection of Cauliflower mosaic virus (CaMV), Turnip mosaic virus (TuMV), Cucumber mosaic virus (CMV) and Alfalfa mosaic virus (AMV) affects seed tolerance to deterioration measuring germination rates after an accelerated aging treatment. Arabidopsis wild type plants infected with AMV and CMV rendered seeds with improved tolerance to deterioration when compared to the non -inoculated plants. On the other hand, CaMV infection generated seeds more sensitive to deterioration. No seeds were obtained from TuMV infected plants. Similar pattern of viral effects was observed in the double mutant athb22 athb25, which is more sensitive to accelerated seed aging than wild type. However, we observed a significant reduction of the seed germination for CMV (65% vs 55%) and healthy (50% vs 30%) plants in these mutants. The seed quality differences were overcomed using the A. thaliana athb25-1D dominant mutant, which over accumulated gibberellic acid (GA), except for TuMV which generated some siliques with low seed tolerance to deterioration. For AMV and TuMV (in athb25-1D), the seed quality correlated with the accumulation of the messengers of the gibberellin 3-oxidase family, the mucilage of the seed and the GA1. For CMV and CaMV it was not a good correlation suggesting that other factors are affecting seed viability. (C) 2017 Elsevier Masson SAS. All rights reserved.We thank L. Corachan and I. Martinez for their excellent technical assistance. This work was supported by grant BI02014-54862-R from the Spanish Direccion General de Investigacion Cientifica y Tecnica (DGICYT) and the Prometeo Program GV2014/010 from the Generalitat Valenciana.Bueso Rodenas, E.; Serrano Salom, R.; Pallas, V.; Sanchez Navarro, JA. (2017). Seed tolerance to deterioration in arabidopsis is affected by virus infection. Plant Physiology and Biochemistry. 116:1-8. https://doi.org/10.1016/j.plaphy.2017.04.020S1811

Uncovering salt tolerance mechanisms in pepper plants: a physiological and transcriptomic approach.

[EN] Background Pepper is one of the most cultivated crops worldwide, but is sensitive to salinity. This sensitivity is dependent on varieties and our knowledge about how they can face such stress is limited, mainly according to a molecular point of view. This is the main reason why we decided to develop this transcriptomic analysis. Tolerant and sensitive accessions, respectively called A25 and A6, were grown for 14 days under control conditions and irrigated with 70 mM of NaCl. Biomass, different physiological parameters and differentially expressed genes were analysed to give response to differential salinity mechanisms between both accessions. Results The genetic changes found between the accessions under both control and stress conditions could explain the physiological behaviour in A25 by the decrease of osmotic potential that could be due mainly to an increase in potassium and proline accumulation, improved growth (e.g. expansins), more efficient starch accumulation (e.g. BAM1), ion homeostasis (e.g. CBL9, HAI3, BASS1), photosynthetic protection (e.g. FIB1A, TIL, JAR1) and antioxidant activity (e.g. PSDS3, SnRK2.10). In addition, misregulation of ABA signalling (e.g. HAB1, ERD4, HAI3) and other stress signalling genes (e.g. JAR1) would appear crucial to explain the different sensitivity to NaCl in both accessions. Conclusions After analysing the physiological behaviour and transcriptomic results, we have concluded that A25 accession utilizes different strategies to cope better salt stress, being ABA-signalling a pivotal point of regulation. However, other strategies, such as the decrease in osmotic potential to preserve water status in leaves seem to be important to explain the defence response to salinity in pepper A25 plants.This work was financed by the INIA (Spain) and the Ministerio de Ciencia, Innovacion y Universidades (RTA2017-00030-C02-00) and the European Regional Development Fund (ERDF). Lidia Lopez-Serrano is a beneficiary of a doctoral fellowship (FPI-INIA).Lopez-Serrano, L.; Calatayud, Á.; López Galarza, SV.; Serrano Salom, R.; Bueso Rodenas, E. (2021). Uncovering salt tolerance mechanisms in pepper plants: a physiological and transcriptomic approach. BMC Plant Biology. 21(1):1-17. https://doi.org/10.1186/s12870-021-02938-2S11721

PRX2 and PRX25, peroxidases regulated by COG1, are involved in seed longevity in Arabidopsis

[EN] Permeability is a crucial trait that affects seed longevity and is regulated by different polymers including proanthocyanidins, suberin, cutin and lignin located in the seed coat. By testing mutants in suberin transport and biosynthesis, we demonstrate the importance of this biopolymer to cope with seed deterioration. Transcriptomic analysis of cog1-2D, a gain-of-function mutant with increased seed longevity, revealed the upregulation of several peroxidase genes. Reverse genetics analysing seed longevity uncovered redundancy within the seed coat peroxidase gene family; however, after controlled deterioration treatment, seeds from the prx2 prx25 double and prx2 prx25 prx71 triple mutant plants presented lower germination than wild-type plants. Transmission electron microscopy analysis of the seed coat of these mutants showed a thinner palisade layer, but no changes were observed in proanthocyanidin accumulation or in the cuticle layer. Spectrophotometric quantification of acetyl bromide-soluble lignin components indicated changes in the amount of total polyphenolics derived from suberin and/or lignin in the mutant seeds. Finally, the increased seed coat permeability to tetrazolium salts observed in the prx2 prx25 and prx2 prx25 prx71 mutant lines suggested that the lower permeability of the seed coats caused by altered polyphenolics is likely to be the main reason explaining their reduced seed longevityRenard, J.; Martínez-Almonacid, I.; Sonntag, A.; Molina, I.; Moya-Cuevas, J.; Bissoli, G.; Muñoz-Bertomeu, J.... (2020). PRX2 and PRX25, peroxidases regulated by COG1, are involved in seed longevity in Arabidopsis. Plant Cell & Environment. 43(2):315-326. https://doi.org/10.1111/pce.13656S315326432Almagro, L., Gómez Ros, L. V., Belchi-Navarro, S., Bru, R., Ros Barceló, A., & Pedreño, M. A. (2008). Class III peroxidases in plant defence reactions. 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A., Summerhurst, D. K., & Razem, F. A. (2004). Oxidases, peroxidases and hydrogen peroxide: The suberin connection. Phytochemistry Reviews, 3(1-2), 113-126. doi:10.1023/b:phyt.0000047810.10706.46Bolger, A. M., Lohse, M., & Usadel, B. (2014). Trimmomatic: a flexible trimmer for Illumina sequence data. Bioinformatics, 30(15), 2114-2120. doi:10.1093/bioinformatics/btu170Bueso, E., Muñoz-Bertomeu, J., Campos, F., Brunaud, V., Martínez, L., Sayas, E., … Serrano, R. (2013). ARABIDOPSIS THALIANA HOMEOBOX25 Uncovers a Role for Gibberellins in Seed Longevity. Plant Physiology, 164(2), 999-1010. doi:10.1104/pp.113.232223Châtelain, E., Satour, P., Laugier, E., Ly Vu, B., Payet, N., Rey, P., & Montrichard, F. (2013). Evidence for participation of the methionine sulfoxide reductase repair system in plant seed longevity. Proceedings of the National Academy of Sciences, 110(9), 3633-3638. doi:10.1073/pnas.1220589110Clerkx, E. J. M., Blankestijn-De Vries, H., Ruys, G. J., Groot, S. P. 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A Tomato Peroxidase Involved in the Synthesis of Lignin and Suberin. Plant Physiology, 122(4), 1119-1128. doi:10.1104/pp.122.4.1119Rains, M. K., Gardiyehewa de Silva, N. D., & Molina, I. (2017). Reconstructing the suberin pathway in poplar by chemical and transcriptomic analysis of bark tissues. Tree Physiology, 38(3), 340-361. doi:10.1093/treephys/tpx060Russell, W. R., Burkitt, M. J., Scobbie, L., & Chesson, A. (2005). EPR Investigation into the Effects of Substrate Structure on Peroxidase-Catalyzed Phenylpropanoid Oxidation. Biomacromolecules, 7(1), 268-273. doi:10.1021/bm050636oSano, N., Rajjou, L., North, H. M., Debeaujon, I., Marion-Poll, A., & Seo, M. (2015). Staying Alive: Molecular Aspects of Seed Longevity. Plant and Cell Physiology, 57(4), 660-674. doi:10.1093/pcp/pcv186Shigeto, J., Itoh, Y., Hirao, S., Ohira, K., Fujita, K., & Tsutsumi, Y. (2015). Simultaneously disrupting AtPrx2 , AtPrx25 and AtPrx71 alters lignin content and structure in Arabidopsis stem. 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Kaempferol-3-rhamnoside overaccumulation in flavonoid 3'-hydroxylase tt7 mutants compromises seed coat outer integument differentiation and seed longevity

[EN] Seeds slowly accumulate damage during storage, which ultimately results in germination failure. The seed coat protects the embryo from the external environment, and its composition is critical for seed longevity. Flavonols accumulate in the outer integument. The link between flavonol composition and outer integument development has not been explored.Genetic, molecular and ultrastructural assays on loss-of-function mutants of the flavonoid biosynthesis pathway were used to study the effect of altered flavonoid composition on seed coat development and seed longevity.Controlled deterioration assays indicate that loss of function of the flavonoid 3 ' hydroxylase gene TT7 dramatically affects seed longevity and seed coat development. Outer integument differentiation is compromised from 9 d after pollination in tt7 developing seeds, resulting in a defective suberin layer and incomplete degradation of seed coat starch. These distinctive phenotypes are not shared by other mutants showing abnormal flavonoid composition. Genetic analysis indicates that overaccumulation of kaempferol-3-rhamnoside is mainly responsible for the observed phenotypes. Expression profiling suggests that multiple cellular processes are altered in the tt7 mutant.Overaccumulation of kaempferol-3-rhamnoside in the seed coat compromises normal seed coat development. This observation positions TRANSPARENT TESTA 7 and the UGT78D1 glycosyltransferase, catalysing flavonol 3-O-rhamnosylation, as essential players in the modulation of seed longevity.This study was funded by the Spanish Ministry of Science and Education, action BIO2014-52621-R and Vicerrectorado de Investigacion UPV (PAID-11-21). Funding for open access charge: CRUE-Universitat Politecnica de Valencia. We thank Dr Javier Forment from the Bioinformatic Unit at the IBMCP for assistance. We thank Alix Mertens and Juliette de Lhonneux for their help in iodine assays, VA Ariza and Raquel Berti for assistance in tt7 phenotyping assays and Dr Dolores Planes and Carmen Ruiz-Pastor for occasional assistance in this study during the COVID-19 pandemic. We thank Dr Anthony Schaeffner, Dr Sebastian Streb and Dr Isabelle Debeaujon for kindly sharing Arabidopsis mutant lines, and Dr Lynne Yenush for critical reading of the manuscript.Niñoles Rodenes, R.; Arjona, P.; Azad, SM.; Hashim, A.; Casañ-Perello, J.; Bueso Rodenas, E.; Serrano, R.... (2023). Kaempferol-3-rhamnoside overaccumulation in flavonoid 3'-hydroxylase tt7 mutants compromises seed coat outer integument differentiation and seed longevity. New Phytologist. 238(4):1461-1478. https://doi.org/10.1111/nph.1883614611478238

Transcription Factor DOF4.1 Regulates Seed Longevity in Arabidopsis via Seed Permeability and Modulation of Seed Storage Protein Accumulation

[EN] Seed longevity is modulated by multiple genetic factors in Arabidopsis thaliana. A previous genome-wide association study using the Elevated Partial Pressure of Oxygen (EPPO) aging assay pinpointed a genetic locus associated with this trait. Reverse genetics identified the transcription factor DOF4.1 as a novel seed longevity factor. dof4.1 loss-of-function plants generate seeds exhibiting higher germination after accelerated aging assays. DOF4.1 is expressed during seed development and RNAseq data show several putative factors that could contribute to the dof4.1 seed longevity phenotype. dof4.1 has reduced seed permeability and a higher levels of seed storage proteins mRNAs (cruciferins and napins) in developing seeds, as compared to wild-type seeds. It has been reported that mutant lines defective in cruciferins or napins present reduced seed longevity. The improved longevity of dof4.1 is totally lost in the quadruple mutant dof4.1 cra crb crc, but not in a dof4.1 line depleted of napins, suggesting a prominent role for cruciferins in this process. Moreover, a negative regulation of DOF4.1 expression by the transcription factor DOF1.8 is suggested by co-inoculation assays in Nicotiana benthamiana. Indeed, DOF1.8 expression anticorrelates with that of DOF4.1 during seed development. In summary, modulation of DOF4.1 levels during seed development contributes to regulate seed longevity.This study was funded by the Spanish Ministry of Science and Education, action BIO2014-52621-R.Niñoles Rodenes, R.; Ruiz-Pastor, CM.; Arjona-Mudarra, P.; Casañ-Perello, J.; Renard, J.; Bueso Rodenas, E.; Mateos, R.... (2022). Transcription Factor DOF4.1 Regulates Seed Longevity in Arabidopsis via Seed Permeability and Modulation of Seed Storage Protein Accumulation. Frontiers in Plant Science. 13:1-14. https://doi.org/10.3389/fpls.2022.9151841141

Seed coat lignification level is crucial in Capsicum spp seed longevity

[EN] Capsicum (pepper) is known for its poor seed germination, particularly seed longevity is usually much shorter than other Solanaceae. However, the molecular mechanisms involved are mostly unknown in these species. The present study examines the differences in seed longevity among Capsicum species and varietal types. Feral or less domesticated species, such as Capsicum chinense and particularly Capsicum frutescens, showed higher germination rates than the more domesticated Capsicum annuum after accelerated seed aging treatments. In addition, variability was detected in the expression of genes involved in the response to seed deterioration. The differences observed in ASPG1 expression led us to study the seed protein profile in dry and germinating seeds. Seed storage protein mobilization during germination was faster in seed aging-resistant genotypes. Similarly, the transcriptional change observed for the orthologous gene of the trans-species regulator AtHB25 prompted us to study the structure and molecular components of the seed coat in peppers. All the Capsicum pepper accessions analyzed presented very lignified testa and we observed a positive correlation between the amount of lignin and seed viability. Our results provide essential information to explain the poor germination observed in pepper seeds and provide an experimental framework for future improvements in this important characterThe authors want to thank Marisol Gascon of the microscope service at the IBMCP. This work has been partially financed by the project PID2019-110221RR-C32, FEDER/ERDF funds.Bissoli, G.; Bono, M.; Martinez-Almonacid, I.; Moreno Peris, E.; Renard, J.; Espinosa, A.; Naranjo, MA.... (2022). Seed coat lignification level is crucial in Capsicum spp seed longevity. Physiologia Plantarum. 174(1):1-9. https://doi.org/10.1111/ppl.13600S19174