Expression analysis of vernalization and day-length response genes in barley (Hordeum vulgare L.) indicates that VRNH2 is a repressor of PPDH2 (HvFT3) under long days

38 Pag., 1 Tabl., 6 Fig.The response to vernalization and the expression of genes associated with responses to vernalization (VRNH1, VRNH2, and VRNH3) and photoperiod (PPDH1 and PPDH2) were analysed in four barley (Hordeum vulgare L.) lines: ‘Alexis’ (spring), ‘Plaisant’ (winter), SBCC058, and SBCC106 (Spanish inbred lines), grown under conditions of vernalization and short days (VSD) or no vernalization and long days (NVLD). The four genotypes differ in VRNH1. Their growth habits and responses to vernalization correlated with the level of expression of VRNH1 and the length of intron 1. ‘Alexis’ and ‘Plaisant’ behaved as expected. SBCC058 and SBCC106 showed an intermediate growth habit and flowered relatively late in the absence of vernalization. VRNH1 expression was induced by cold for all genotypes. Under VSD, VRNH1 expression was detected in the SBCC genotypes later than in ‘Alexis’ but earlier than in ‘Plaisant’. VRNH2 was repressed under short days while VRNH1 expression increased in parallel. VRNH3 was detected only in ‘Alexis’ under NVLD, whereas it was not expressed in plants with the active allele of VRNH2 (SBCC058 and ‘Plaisant’). Under VSD, PPDH2 was expressed in ‘Alexis’, SBCC058, and SBCC106, but it was only expressed weakly in ‘Alexis’ under NVLD. Further analysis of PPDH2 expression in two barley doubled haploid populations revealed that, under long days, HvFT3 and VRNH2 expression levels were related inversely. The timing of VRNH2 expression under a long photoperiod suggests that this gene might be involved in repression of PPDH2 and, indirectly, in the regulation of flowering time through an interaction with the day-length pathway.This study was funded by grants AGL2007-63625 and HH2008-0013 from the Spanish Ministry of Science and Technology and by the European Regional Development Fund. Germplasm from the SBCC is maintained with funding from project RFP2004-00015-00-00. MCC was supported by an I3P Predoctoral Fellowship from CSIC.Peer reviewe

Expresión, regulación y diversidad de genes de respuesta a la temperatura y el fotoperiodo en cebada (Hordeum vulgare L.)

222 Pags., con Tabls. y Figs.[ES] La duración de las distintas fases de desarrollo de la planta y su adecuación a las condiciones ambientales representan algunos de los caracteres fundamentales de adaptación de los cereales. Uno de los momentos más importantes en el desarrollo de los cereales, con mayor repercusión en el rendimiento, es la fecha de floración. Diversos estudios recientes han identificado los genes responsables de las respuestas a los estímulos ambientales que regulan la floración. Estos estímulos son, sobre todo, la longitud del día y la temperatura, especialmente la vernalización, o necesidad de un periodo frío para que se produzca un progreso normal hacia la floración. Según las respuestas que producen y las fechas de siembra recomendadas, los cereales como la cebada o el trigo se suelen dividir en variedades de invierno y de primavera. En este trabajo, se estudia la diversidad alélica y funcional de varios genes (VRNH1, VRNH2, VRNH3, PPDH1 y PPDH2). Concretamente, se analizan los efectos fenotípicos, los patrones de expresión génica y la regulación de los genes más importantes de las rutas de la vernalización y el fotoperiodo. Esta tesis se basa en buena medida en el estudio de material vegetal autóctono de la zona mediterránea, asumiendo que posee mecanismos de adaptación seleccionados a lo largo de siglos de cultivo. Los genotipos tradicionales estudiados proceden de la Colección Nuclear de Cebadas Españolas (CNCE), que es una representación del rango de variación del germoplasma de cebada tradicionalmente cultivado en España.[EN] The duration of the different stages of plant development, and their adjustment to environmental conditions are essential for adaptation in cereals. One of the most important moments in the development of cereals, with the greatest impact on grain yield, is the date of flowering. Recent studies have identified the genes responsible for responses to environmental stimuli that regulate flowering. These stimuli are, mainly, day-length and temperature. Vernalization, particularly, is the need of a cold period to allow a normal progress of the plant towards flowering. According to the phenotypic responses produced and recommended planting dates, cereals such as barley and wheat are divided into winter and spring varieties. In this work, we studied the allelic diversity of several functional genes (VRNH1, VRNH2, VRNH3, PPDH1 and PPDH2). Specifically, we analyze the phenotypic effects, patterns of gene expression and regulation of the most important genes which respond to vernalization and photoperiod. This thesis is based largely on the study of plant material indigenous to the Mediterranean area, assuming that they bear adaptation traits that have been selected over centuries of cultivation. The indigenous materials studied come from the Spanish Barley Core Collection (SBCC), which is a representation of the range of variation of barley germplasm grown traditionally in Spain.Esta tesis se realizó gracias a una beca predoctoral de programa I3P del Consejo Superior de Investigaciones Científicas (CSIC) y a la financiación de los proyectos de Plan Nacional de I+D+I AGL2004-05311/AGR y AGL2007-63625/AGR.Peer reviewe

Adaptation of barley to mild winters: A role for PPDH2

39 Pags., 3 Tabls., 4 Figs. The definitive version is available at: http://www.biomedcentral.com/bmcplantbiolBackground Understanding the adaptation of cereals to environmental conditions is one of the key areas in which plant science can contribute to tackling challenges presented by climate change. Temperature and day length are the main environmental regulators of flowering and drivers of adaptation in temperate cereals. The major genes that control flowering time in barley in response to environmental cues are VRNH1, VRNH2, VRNH3, PPDH1, and PPDH2 (candidate gene HvFT3). These genes from the vernalization and photoperiod pathways show complex interactions to promote flowering that are still not understood fully. In particular, PPDH2 function is assumed to be limited to the ability of a short photoperiod to promote flowering. Evidence from the fields of biodiversity, ecogeography, agronomy, and molecular genetics was combined to obtain a more complete overview of the potential role of PPDH2 in environmental adaptation in barley. Results The dominant PPDH2 allele is represented widely in spring barley cultivars but is found only occasionally in modern winter cultivars that have strong vernalization requirements. However, old landraces from the Iberian Peninsula, which also have a vernalization requirement, possess this allele at a much higher frequency than modern winter barley cultivars. Under field conditions in which the vernalization requirement of winter cultivars is not satisfied, the dominant PPDH2 allele promotes flowering, even under increasing photoperiods above 12 h. This hypothesis was supported by expression analysis of vernalization-responsive genotypes. When the dominant allele of PPDH2 was expressed, this was associated with enhanced levels of VRNH1 and VRNH3 expression. Expression of these two genes is needed for the induction of flowering. Therefore, both in the field and under controlled conditions, PPDH2 has an effect of promotion of flowering. Conclusions The dominant, ancestral, allele of PPDH2 is prevalent in southern European barley germplasm. The presence of the dominant allele is associated with early expression of VRNH1 and early flowering. We propose that PPDH2 promotes flowering of winter cultivars under all non-inductive conditions, i.e. under short days or long days in plants that have not satisfied their vernalization requirement. This mechanism is indicated to be a component of an adaptation syndrome of barley to Mediterranean conditions.This study was funded by grants AGL2007-63625, AGL2010-21929, and HH2008-0013 from the Spanish Ministry of Science and Technology, by the European Regional Development Fund, and by the Hungarian Scientific Research Fund (OTKA NK72913). Germplasm from the SBCC is maintained with funding from projects RFP2004-00015-00-00 and RFP2009-00005-00-00. MCC was supported by an I3P Predoctoral Fellowship from CSIC.Peer reviewe

Barley adaptation. Lessons learned from landraces will help to cope with climate change

27 Pags., with Figs. y Tabls.Adaptation of crops to temperate climates depends to a large extent on plants having the appropriate combination of genes to respond to environmental cues. Global warming poses new challenges to plant breeding. In many places, current cultivars will no longer be suited for cultivation. We present several findings on barley adaptation to Mediterranean climates, which resulted from the study of adaptations presented by local landraces. Winter barley is widely grown in the Mediterranean region. We found that local winter landraces have some degree of vernalization requirement, tuned to respond to the winter temperatures typical for each region. Our results demonstrate that the allelic series of the main vernalization gene, VrnH1, is essential to determine the length of the cold period needed to promote flowering in barley. The presence of photoperiod gene HvFT3 in most Mediterranean landraces is presented as a safety mechanism to promote flowering, which comes into play at least when vernalization conditions are not optimum (rather often in some areas). This mechanism is coordinated with the vernalization pathway through repression by VrnH2. A latitudinal pattern of distribution of HvFT1 in Spanish barleys suggests a role in adaptation. This gene integrates the photoperiod and vernalization pathways in barley, and seems to present an allelic series of at least five functionally different alleles. We present evidences from several independent sets of materials that demonstrate the effect of three of these alelles, in accordance with the latitudinal distribution observed. A combination of these three mechanisms optimizes the growth cycle of Mediterranean landraces. These mechanisms have a wider interest in a climate change scenario, as temperatures in most of Europe will increase, and may become beneficial in higher latitudes. Cultivars with new combinations of vernalization, photoperiod and frost tolerance alleles will have to be bred for the upcoming conditions.Funded by Spanish Ministries of Economy and Competitiveness (former Science and Innovation) and Agriculture.Peer reviewe

Introgression of an intermediate VRNH1 allele in barley (Hordeum vulgare L.) leads to reduced vernalization requirement without affecting freezing tolerance

26 Pag., 2 Tabl., 4 Fig. The definitive version is available at: http://www.springerlink.com/content/1380-3743/The process of vernalization is mainly controlled by two genes in winter barley (Hordeum vulgare L.), VRNH1 and VRNH2. A recessive allele at VRNH1 and a dominant allele at VRNH2 must be present to induce a vernalization requirement. In addition, this process is usually associated with greater low-temperature tolerance. Spanish barleys originated in areas with mild winters and display a reduced vernalization requirement compared with standard winter cultivars. The objective of this study was to investigate the genetic origin of this reduced vernalization requirement and its effect on frost tolerance. We introgressed the regions of a typical Spanish barley line that carry VRNH1 and VRNH2 into a winter cultivar, Plaisant, using marker-assisted backcrossing. We present the results of a set of 12 lines introgressed with all four possible combinations of VRNH1 and VRNH2, which were evaluated for vernalization requirement and frost tolerance. The reduced vernalization requirement of the Spanish parent was confirmed, and was found to be due completely to the effect of the VRNH1 region. The backcross lines showed no decline in frost tolerance compared with that of the recurrent parent unless they carried an extra segment of chromosome 5H. This extra segment, a carryover of the backcross process, apparently contained the well-known frost tolerance quantitative trait locus Fr-H2. We demonstrate that it is possible to manipulate the vernalization requirement with only minor effects on frost tolerance. This finding opens the path to creating new types of barley cultivars that are better suited to specific environments, especially in a climate-change scenario.This work was funded by the Spanish Ministry of Science and Innovation (projects AGL2004-05311, GEN2006-28560-E, and AGL2007-63625), and co-funded by the European Regional Development Fund. CC was supported by an I3P predoctoral fellowship from CSIC.Peer reviewe