Chloride regulates leaf cell size and water relations in tobacco plants

19 páginas.-- 9 figuras.-- 5 tablas.-- 77 referencias.-- Supplementary Data: Supplementary_figures_S1_S7___Tables_S1_S7.pdfChloride (Cl–) is a micronutrient that accumulates to macronutrient levels since it is normally available in nature and actively taken up by higher plants. Besides a role as an unspecific cell osmoticum, no clear biological roles have been explicitly associated with Cl– when accumulated to macronutrient concentrations. To address this question, the glycophyte tobacco (Nicotiana tabacum L. var. Habana) has been treated with a basal nutrient solution supplemented with one of three salt combinations containing the same cationic balance: Cl–-based (CL), nitrate-based (N), and sulphate+phosphate-based (SP) treatments. Under non-saline conditions (up to 5mM Cl–) and no water limitation, Cl– specifically stimulated higher leaf cell size and led to a moderate increase of plant fresh and dry biomass mainly due to higher shoot expansion. When applied in the 1–5mM range, Cl– played specific roles in regulating leaf osmotic potential and turgor, allowing plants to improve leaf water balance parameters. In addition, Cl– also altered water relations at the whole-plant level through reduction of plant transpiration. This was a consequence of a lower stomatal conductance, which resulted in lower water loss and greater photosynthetic and integrated water-use efficiency. In contrast to Cl–, these effects were not observed for essential anionic macronutrients such as nitrate, sulphate, and phosphate. We propose that the abundant uptake and accumulation of Cl– responds to adaptive functions improving water homeostasis in higher plants.This work was supported by the Spanish Ministry of Science and Innovation-FEDER grant AGL2009-08339/AGR. The help, expertise, and technical assistance of C. Rivero, A. Vázquez, S. Luque, B.J. Sañudo, F.J. Durán, Y. Pinto, and J. Espartero are gratefully acknowledged. We would like to extend our gratitude to the valuable reviews and contributions by the anonymous referees and the editor, Timothy Colmer, which helped us to improve the manuscript substantially.Peer reviewe

Chloride Nutrition Regulates development, Water Balance and Drought Resistance in Plants

6 páginas.-- 5 figuras.-- 9 referencias.-- Poster presentado en el XII Luso-Spanish Symposium on Plant Water Relations – Water to Feed the World. 30th of September – 3rd of October (Evora) PortugalCl- is a strange micronutrient since actual Cl- concentration in plants is about two orders of magnitude higher than the content required as essential micronutrient. This accumulation requires a high cost of energy, and since Cl- is a major osmotically active solute in the vacuole, we propose that Cl- plays a role in the regulation of water balance in plants. We show here that, when accumulated to macronutrient levels, Cl- specifically regulates leaf cell elongation and water balance parameters, improving water relations at both the leaf tissue and the whole plant levels, increasing drought resistance in higher plants.This work was supported by the Spanish Ministry of Science and Innovation-FEDER grant AGL2009-08339/AGR.Peer Reviewe

Vision, challenges and opportunities for a Plant Cell Atlas

With growing populations and pressing environmental problems, future economies will be increasingly plant-based. Now is the time to reimagine plant science as a critical component of fundamental science, agriculture, environmental stewardship, energy, technology and healthcare. This effort requires a conceptual and technological framework to identify and map all cell types, and to comprehensively annotate the localization and organization of molecules at cellular and tissue levels. This framework, called the Plant Cell Atlas (PCA), will be critical for understanding and engineering plant development, physiology and environmental responses. A workshop was convened to discuss the purpose and utility of such an initiative, resulting in a roadmap that acknowledges the current knowledge gaps and technical challenges, and underscores how the PCA initiative can help to overcome them.National Science Foundation 1916797 David W Ehrhardt, Kenneth D Birnbaum, Seung Yon Rhee; National Science Foundation 2052590 Seung Yon Rhe

Chloride nutrition at macronutrient levels regulates plant development, water balance and drought resistance of tobacco plants

Chloride (Cl-) is considered to be a strange micronutrient since actual Cl- concentrations in plants is 10-100 times higher than the content required as essential micronutrient, (Marschner, 1995; Brumós et al, 2010), whereas all the other mineral micronutrients (B, Cu, Fe, Mn, Mo, Ni, Zn) are present at much lower concentrations in plant tissues (1-5 orders of magnitude below). Since Cl- uptake and transport is an energetically expensive process (White and Broadley 2001; Brumós et al, 2010), we propose that Cl-, when accumulated to concentrations typical of the content of a macronutrient, plays a poorly understood biological role, not critical under normal growth conditions. Since Cl- appears to be particularly well suited to accomplish osmoregulatory functions, the proposed biological role could be related to the regulation of water balance at both the cell and the whole plant level. There is little experimental evidence in this regard since: i) it is unclear in which extent Cl- is specifically required to fulfil osmoregulatory roles or whether other anions, like nitrate, phosphate, sulphate, and organic acids can replace chloride in such functions; ii) usually the role of Cl- is not adequately differentiated from that of their accompanying cations; iii) the concepts linking Cl- homeostasis with osmotic/turgor regulation have been frequently discussed in the context of halophyte species and in glycophytes under salt stress conditions (Flowers et al, 1988), what have led to some confusion in the context of Cl- nutrition. We intend to establish the role of Cl- in glycophyte plants when accumulated to macronutrient levels, and we will present results showing that under non-saline conditions (1-5 mM external Cl- concentrations) and no water limitation, Cl- specifically promotes the growth of tobacco plants through mechanisms regulating leaf cell elongation and water relations. Furthermore, under water deficit conditions, Cl--treated plants exhibit drought resistance due to the sum of stress avoidance (reduced estomatal water loss) and tolerance (probably due to higher solute accumulation) mechanisms. - Brumós J., Talón M., Bouhlal R.Y.M. & Colmenero-Flores J.M. (2010) Cl- homeostasis in includer and excluder citrus rootstocks: transport mechanisms and identification of candidate genes. Plant Cell Env, 33, 2012-2027. - Marschner H. (1995) Mineral Nutrition of Higher Plants, 2nd ed. (Second Edition ed.). Academic Press, London. - Flowers T.J. (1988) Chloride as a nutrient and as an osmoticum. In: Advances in plant nutrition (ed L.A. Tinker B), pp. 55-78. Praeger, New York.ENVIRONMENT WORKSHOPS 2013 “GENOMIC, PHYSIOLOGICAL AND BREEDING APPROAHES FOR ENHANCING DROUGHT RESISTANCE IN CROPS ” Baeza, Spain, 23–25 September 2013Peer Reviewe

Changes in transcriptional profiles of mature and immature citrus leaves acclimated to salinity

Poster presentado en the XII International Citrus Congress. Valencia, Spain 18th–23rd November 2012While the molecular response of salinized plants in the short-medium term (hours-days) has been broadly studied, the knowledge about the nature of the genes involved in maintaining homeostatic conditions the long term (months-years) has remained elusive. With this aim, we have analyzed the transcriptome of leaves from citrus plants acclimated to moderate salinity (2 years with NaCl 30 mM). Through functional genomics, using the 7K cDNA chip from ¿Consorcio Valenciano de Genómica Funcional de Cítricos¿, the transcriptome of citrus plants acclimatized to salinity was analyzed in mature leaves (8 months) and immature leaves (2 months). Although immature leaves accumulated low levels of chloride (0.51%±0.06), they exhibited high responsiveness to salinity (1,211 differential-responsive genes) compared with mature leaves, which cumulated higher chloride levels (1.05% ± 0.01), and showed a lower number of differentially-responsive genes (100 genes). Immature leaves induced functional categories that were not induced in mature leaves, like ¿cell wall biosynthesis¿, ¿metabolism¿, ¿defense¿, ¿secretion and membrane traffic¿, ¿water transport¿ and ¿antioxidant activity¿. On the other hand, the degree of coincidence was higher in the group of genes that were repressed by salinity. Both mature and immature leaves repressed genes mostly involved in ¿stress response¿. We highlight how the same plant organ in different developmental stages show huge differences in the amount and nature of genes which are responding to an abiotic stimulus.Peer Reviewe

Chloride Nutrition: Novel Functions in Water Relations

4 páginas.-- 3 figuras.-- 11 referencias.-- Póster presentado en el XI Simposio Hispano-Portugués de Relaciones Hídricas en las Plantas, Sevilla 17-20 Sep. (2012)Although Cl- has been characterized as a micronutrient, we have observed that when available in the millimolar range (e.g. 1-5 mM), higher plants accumulate Cl- to levels that are typical of the content of a macronutrient (Plant Cell Env. 2010, 33: 2012-27). Since this requires a considerable cost of energy, we speculate whether Cl- might play a poorly understood function in plants when accumulated to macronutrient levels. Given that Cl- is a major osmotically active solute in the plant vacuole, we propose that this element alter plant water relation mechanisms. Besides promoting plant growth and dry weight, we observed that chloride nutrition in the millimolar range improved water parameters like the relative water content, leaf succulence and water use efficiency. Under conditions of water deficit chloride-treated plants exhibited an improved regulation of the water balance and drought-tolerance. According to the data obtained, we propose that critical factors behind these phenomena are an improved osmotic regulation, a reduced transpiration and developmental alterations.This work was financed by ‘MICINN’ (AGL2009-08339; Spain)Peer Reviewe

Transcriptional profile analysis of young and mature leaves of citrus trees acclimated to salinity

11 páginas.-- 3 figuras.-- 2 tablas.-- 32 referencias.-- Artículo publicado en XII International Citrus Congress - International Society of CitricultureWhile the molecular response of model plants to salt stress in the short-medium term (hours-days) has been broadly studied, the knowledge about the nature of genes involved in maintaining homeostatic conditions in the long term (months-years) in woody perennial trees has not been addressed yet. We have analyzed physiological parameters and the transcriptome profiles of photosynthetically active leaves from citrus trees acclimatized to moderate salinity (NaCl 30 mM) after 2 years treatment. Through functional genomics, global gene expression in response to NaCl treatment in mature (8 months-old) and young (2 months-old) leaves has been analyzed and compared. Although young leaves (YL) accumulated low levels of chloride (0.51%±0.06), they exhibited a much stronger response to salinity in term of the number of differentially expressed genes (1,211 genes) compared with mature leaves (ML), which accumulated higher chloride levels (1.05%±0.01), and exhibited a much lower number of differentially-responsive genes (100 genes). In this work, a number of responses have been observed that differ from those described in previous studies of citrus plants non-acclimatized to salt stress (Brumos et al., 2009), whose principal manifestation was the lack of repression of primary metabolism in leaves at the molecular and physiological levels. Results describing enriched functional categories of differentially expressed genes are presented and discussed highlighting how the long-term acclimation to NaCl stress involves drastically different molecular strategies depending on the developmental stage of plant leaves.This work was partially supported by the Spanish Ministry of Science and Innovation projects AGL2007-6537-C04-04 and PS-060000-2009-7, and the European Social and FEDER Funds for financial support. Juan G. Pérez-Pérez acknowledges the ‘Instituto Nacional de Investigaciones Agrarias’ for a PhD fellowship to support his research.Peer reviewe

Membrane transporters and carbon metabolism implicated in chloride homeostasis differentiate salt stress responses in tolerant and sensitive Citrus rootstocks

17 pages, 6 figures, 1 table, 72 references. Help and expertise of A. Almenar, A. Boix, A. López, E. Blázquez, I. López, I. Sanchís, and M. Sancho are gratefully acknowledged.Salinity tolerance in Citrus is strongly related to leaf chloride accumulation. Both chloride homeostasis and specific genetic responses to Cl- toxicity are issues scarcely investigated in plants. To discriminate the transcriptomic network related to Cl- toxicity and salinity tolerance, we have used two Cl- salt treatments (NaCl and KCl) to perform a comparative microarray approach on two Citrus genotypes, the salt-sensitive Carrizo citrange, a poor Cl- excluder, and the tolerant Cleopatra mandarin, an efficient Cl- excluder. The data indicated that Cl- toxicity, rather than Na+ toxicity and/or the concomitant osmotic perturbation, is the primary factor involved in the molecular responses of citrus plant leaves to salinity. A number of uncharacterized membrane transporter genes, like NRT1-2, were differentially regulated in the tolerant and the sensitive genotypes, suggesting its potential implication in Cl- homeostasis. Analyses of enriched functional categories showed that the tolerant rootstock induced wider stress responses in gene expression while repressing central metabolic processes such as photosynthesis and carbon utilization. These features were in agreement with phenotypic changes in the patterns of photosynthesis, transpiration, and stomatal conductance and support the concept that regulation of transpiration and its associated metabolic adjustments configure an adaptive response to salinity that reduces Cl- accumulation in the tolerant genotype.Work at Centro de Genómica was supported by INCO UE project 015453 and Ministerio de Educación y Ciencia- FEDER grant AGL2007-65437-C04-01/AGR.Peer reviewe

Large changes in anatomy and physiology between diploid Rangpur lime (Citrus limonia) and its autotetraploid are not associated with large changes in leaf gene expression

13 pages, 5 figures, 4 tables, 75 references. We thank Angel Boix for technical assistance.Very little is known about the molecular origin of the large phenotypic differentiation between genotypes arising from somatic chromosome set doubling and their diploid parents. In this study, the anatomy and physiology of diploid (2x) and autotetraploid (4x) Rangpur lime (Citrus limonia Osbeck) seedlings has been characterized. Growth of 2x was more vigorous than 4x although leaves, stems, and roots of 4x plants were thicker and contained larger cells than 2x that may have a large impact on cell-to-cell water exchanges. Leaf water content was higher in 4x than in 2x. Leaf transcriptome expression using a citrus microarray containing 21 081 genes revealed that the number of genes differentially expressed in both genotypes was less than 1% and the maximum rate of gene expression change within a 2-fold range. Six up-regulated genes in 4x were targeted to validate microarray results by real-time reverse transcription-PCR. Five of these genes were apparently involved in the response to water deficit, suggesting that, in control conditions, the genome expression of citrus autotetraploids may act in a similar way to diploids under water-deficit stress condition. The sixth up-regulated gene which codes for a histone may also play an important role in regulating the transcription of growth processes. These results show that the large phenotypic differentiation in 4x Rangpur lime compared with 2x is not associated with large changes in genome expression. This suggests that, in 4x Rangpur lime, subtle changes in gene expression may be at the origin of the phenotypic differentiation of 4x citrus when compared with 2x.This work was supported by European ‘INCO’ project (FP6- 2003-INCO-DEV-2 no. 015453) to T Allario. Spanish Ministerio de Ciencia e Innovacio´n-FEDER grants (AGL2007- 65437-C04-01, AGL2008-00596/AGR, and AGL2009-08339/ AGR) and a Prometeo 2008/121 Generalidad Valenciana grant provided additional findings.Peer reviewe

Chloride at macronutrient levels increases drought resistance by improving water balance and water-use efficiency

Póster presentado en el SEB’s Annual Meeting 2-5 July (2019) Seville, SpainChloride (Cl-) has been recently described as a beneficial macronutrient in well-irrigated plants, playing specific roles in promoting plant growth, photosynthetic performance and water-use efficiency (WUE). Therefore, a new research framework is opened in the search for adaptive mechanisms that regulate water homeostasis and, in particular, the plant ability to withstand water deficit. Drought is now recognized as the abiotic stress that most importantly affects global crop productivity. Understanding how plants use water for optimal biomass production has become a fundamental issue worldwide. In this work, we aim to elucidate whether Cl- nutrition at macronutrient levels stimulates drought resistance and which physiological mechanisms are involved. To that end, tobacco plants were treated for 30 days with three nutritional treatments added to the basal solution: CL (5 mM Cl-), N (5 mM nitrate), and SP (1.25 mM sulphate and 1.875 mM phosphate), containing all of them the same cationic balance. Then, plants were subjected to two irrigation regimes for 20 days: control (100% field capacity) and moderate drought (60% field capacity). Results showed that, in comparison to SP and N treatments, Cl- application (CL treatment) improved plant growth, leaf development, water balance parameters and WUE under drought conditions. Interestingly, N-treated plants exhibited the strongest growth reduction during drought, showing higher stress symptoms caused by an inefficient water use. Therefore, we propose that the abundant uptake and accumulation of Cl- responds to an adaptive function that improves water relations and drought resistance in higher plants.N