RESUMEN
KEY MESSAGE: The response of a large panel of European elite wheat varieties to post-anthesis heat stress is influenced by 17 QTL linked to grain weight or the stay-green phenotype. Heat stress is a critical abiotic stress for winter bread wheat (Triticum aestivum L.) especially at the flowering and grain filling stages, limiting its growth and productivity in Europe and elsewhere. The breeding of new high-yield and stress-tolerant wheat varieties requires improved understanding of the physiological and genetic bases of heat tolerance. To identify genomic areas associated with plant and grain characteristics under heat stress, a panel of elite European wheat varieties (N = 199) was evaluated under controlled conditions in 2016 and 2017. A split-plot design was used to test the effects of high temperature for ten days after flowering. Flowering time, leaf chlorophyll content, the number of productive spikes, grain number, grain weight and grain size were measured, and the senescence process was modeled. Using genotyping data from a 280 K SNP chip, a genome-wide association study was carried out to test the main effect of each SNP and the effect of SNP × treatment interaction. Genotype × treatment interactions were mainly observed for grain traits measured on the main shoots and tillers. We identified 10 QTLs associated with the main effect of at least one trait and seven QTLs associated with the response to post-anthesis heat stress. Of these, two main QTLs associated with the heat tolerance of thousand-kernel weight were identified on chromosomes 4B and 6B. These QTLs will be useful for breeders to improve grain yield in environments where terminal heat stress is likely to occur.
Asunto(s)
Pan , Triticum , Estudio de Asociación del Genoma Completo , Respuesta al Choque Térmico , Fenotipo , FitomejoramientoRESUMEN
The effects of abscisic acid (ABA) on aquaporin content, root hydraulic conductivity (Lpr), whole plant hydraulic conductance, and leaf growth are controversial. We addressed these effects via a combination of experiments at different scales of plant organization and tested their consistency via a model. We analyzed under moderate water deficit a series of transformed maize (Zea mays) lines, one sense and three antisense, affected in NCED (for 9-cis-epoxycarotenoid dioxygenase) gene expression and that differed in the concentration of ABA in the xylem sap. In roots, the mRNA expression of most aquaporin PIP (for plasma membrane intrinsic protein) genes was increased in sense plants and decreased in antisense plants. The same pattern was observed for the protein contents of four PIPs. This resulted in more than 6-fold differences between lines in Lpr under both hydrostatic and osmotic gradients of water potential. This effect was probably due to differences in aquaporin activity, because it was nearly abolished by a hydrogen peroxide treatment, which blocks the water channel activity of aquaporins. The hydraulic conductance of intact whole plants was affected in the same way when measured either in steady-state conditions or via the rate of recovery of leaf water potential after rewatering. The recoveries of leaf water potential and elongation upon rehydration differed between lines and were accounted for by the experimentally measured Lpr in a model of water transfer. Overall, these results suggest that ABA has long-lasting effects on plant hydraulic properties via aquaporin activity, which contributes to the maintenance of a favorable plant water status.
Asunto(s)
Ácido Abscísico/farmacología , Acuaporinas/metabolismo , Sequías , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/crecimiento & desarrollo , Zea mays/efectos de los fármacos , Zea mays/metabolismo , Ácido Abscísico/biosíntesis , Acuaporinas/genética , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Genes de Plantas , Peróxido de Hidrógeno/farmacología , Hidroponía , Modelos Biológicos , Exudados de Plantas/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/fisiología , Estomas de Plantas/efectos de los fármacos , Estomas de Plantas/fisiología , Transpiración de Plantas/efectos de los fármacos , Plantas Modificadas Genéticamente , Suelo , Factores de Tiempo , Transformación Genética/efectos de los fármacos , Xilema/efectos de los fármacos , Xilema/fisiología , Zea mays/genética , Zea mays/fisiologíaRESUMEN
The role of abscisic acid (ABA) and its possible interaction with ethylene in mediating leaf elongation response to soil water deficit are a matter of controversy. To address this question, we used a set of maize genotypes with various levels of ABA either due to natural variability or to genetic transformation targeted on NCED/VP14, a key enzyme of ABA synthesis. The transgenic lines yielded less strong phenotypes than available mutants, making it possible to use them under normal growing conditions. We focused on leaf elongation during night periods in order to avoid the confounding effect of ABA on leaf water status. Our results suggest that over a wide range, internal ABA level (measured in both leaf extracts or xylem sap) has no clear effect on leaf elongation response to soil water deficit, except in the case of an antisense line presenting the strongest reduction in ABA accumulation that showed a slight maintenance of leaf elongation during water deficit. Leaf ethylene production rate was variable and not related to water deficit except in the ABA-deficient transgenic lines where it was increased by water deficit on average but not systematically. Moreover, variability in ethylene production rate was not linked to variability in elongation rate. Our results thus suggest that neither ABA nor ethylene seems to play a major role in the control of leaf elongation response to soil water deficit.
Asunto(s)
Ácido Abscísico/metabolismo , Etilenos/metabolismo , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Suelo/análisis , Agua/metabolismo , Zea mays/genética , Ácido Abscísico/biosíntesis , Regulación de la Expresión Génica de las Plantas , Variación Genética/genética , Genotipo , Hojas de la Planta/efectos de los fármacos , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Transformación Genética , Agua/farmacología , Zea mays/metabolismoRESUMEN
The isolate AF199 of Lettuce mosaic virus (LMV, genus Potyvirus) causes local lesions followed by systemic wilting and plant death in the lettuce cultivars Ithaca and Vanguard 75. Analysis of the phenotype of virus chimeras revealed that a region within the P1 protein coding region (nucleotides 112-386 in the viral genome) and/or another one within the CI protein coding region (nucleotides 5496-5855) are sufficient together to cause the lethal wilting in Ithaca, but not in Vanguard 75. This indicates that the determinants of this particular symptom are different in these two lettuce cultivars. The wilting phenotype was not directly correlated with differences in the deduced amino acid sequence of these two regions. Furthermore, transient expression of the LMV-AF199 proteins, separately or in combination, did not induce local necrosis or any other visible reaction in the plants. Together, these results suggest that the systemic wilting reaction might be due to RNA rather than protein sequences.
Asunto(s)
Genes Virales , Lactuca/virología , Enfermedades de las Plantas/virología , Potyvirus/genética , Potyvirus/patogenicidad , ARN Helicasas/genética , ARN Helicasas/fisiología , ARN Viral/fisiología , Proteínas Virales/genética , Proteínas Virales/fisiología , Virulencia/genéticaRESUMEN
Lettuce mosaic virus (LMV) isolates LMV-E and LMV-0 differ in their virulence on lettuce varieties carrying the mo1(2) resistance gene, which reduces viral accumulation and blocks the expression of symptoms after infection with avirulent isolates such as LMV-0. Previous work had indicated that reporter genes such as GUS or GFP affect the biological properties of recombinant LMV isolates in both susceptible and resistant lettuce varieties when fused to the N-terminus of the viral protein HC-Pro. The impact of the addition of a cleavage site for the NIa proteinase between the reporter gene and HC-Pro was evaluated, in an effort to recover the full spectrum of the biological properties of parental isolates. Symptoms, accumulation, cell-to-cell and long distance movement of the recombinant viruses containing the NIa cleavage site were studied in susceptible and mo1(2) lettuce varieties. Both LMV-0 and LMV-E recombinant viruses recovered the behaviour of their wild-type parent in susceptible plants upon addition of the NIa cleavage site. While the recombinant LMV-E modified in this way recovered the breaking properties of its wild-type counterpart in mo1(2) plants, similar modification of the LMV-0 derived recombinants failed to rescue a severe inhibition in systemic accumulation in mo1(2) plants, despite the fact that neither cell-to-cell movement nor phloem loading or unloading seemed to be severely affected.