RESUMEN
cis-Regulatory variations contribute to trait evolution and adaptation during crop domestication and improvement. As the most important harvested organ in maize (Zea mays L.), kernel size has undergone intensive selection for size. However, the associations between maize kernel size and cis-regulatory variations remain unclear. We chose two independent association populations to dissect the genetic architecture of maize kernel size together with transcriptomic and genotypic data. The resulting phenotypes reflected a strong influence of population structure on kernel size. Compared with genome-wide association studies (GWASs), which accounted for population structure and relatedness, GWAS based on a naïve or simple linear model revealed additional associated single-nucleotide polymorphisms significantly involved in the conserved pathways controlling seed size in plants. Regulation analyses through expression quantitative trait locus mapping revealed that cis-regulatory variations likely control kernel size by fine-tuning the expression of proximal genes, among which ZmKL1 (GRMZM2G098305) was transgenically validated. We also proved that the pyramiding of the favorable cis-regulatory variations has contributed to the improvement of maize kernel size. Collectively, our results demonstrate that cis-regulatory variations, together with their regulatory genes, provide excellent targets for future maize improvement.
Asunto(s)
Estudio de Asociación del Genoma Completo , Zea mays , Expresión Génica , Genes Reguladores , Fenotipo , Zea mays/metabolismoRESUMEN
In plants, the bZIP (basic leucine zipper) transcription factors regulate diverse functions, including processes such as plant development and stress response. However, few have been functionally characterized in maize (Zea mays). In this study, we cloned ZmbZIP72, a bZIP transcription factor gene from maize, which had only one copy in the maize genome and harbored three introns. Analysis of the amino acid sequence of ZmbZIP72 revealed a highly conserved bZIP DNA-binding domain in its C-terminal region, and four conserved sequences distributed in N- or C-terminal region. The ZmbZIP72 gene expressed differentially in various organs of maize plants and was induced by abscisic acid, high salinity, and drought treatment in seedlings. Subcellular localization analysis in onion epidermal cells indicated that ZmbZIP72 was a nuclear protein. Transactivation assay in yeast demonstrated that ZmbZIP72 functioned as a transcriptional activator and its N terminus (amino acids 23-63) was necessary for the transactivation activity. Heterologous overexpression of ZmbZIP72 improved drought and partial salt tolerance of transgenic Arabidopsis plants, as determined by physiological analyses of leaf water loss, electrolyte leakage, proline content, and survival rate under stress. In addition, the seeds of ZmbZIP72-overexpressing transgenic plants were hypersensitive to ABA and osmotic stress. Moreover, overexpression of ZmbZIP72 enhanced the expression of ABA-inducible genes such as RD29B, RAB18, and HIS1-3. These results suggest that the ZmbZIP72 protein functions as an ABA-dependent transcription factor in positive modulation of abiotic stress tolerance and may be a candidate gene with potential application in molecular breeding to enhance stress tolerance in crops.
Asunto(s)
Arabidopsis/genética , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/metabolismo , Plantas Tolerantes a la Sal/genética , Zea mays/genética , Ácido Abscísico/farmacología , Secuencia de Aminoácidos , Arabidopsis/efectos de los fármacos , Arabidopsis/fisiología , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/clasificación , Factores de Transcripción con Cremalleras de Leucina de Carácter Básico/genética , Clonación Molecular , Secuencia Conservada , Sequías , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Germinación/efectos de los fármacos , Datos de Secuencia Molecular , Cebollas/genética , Cebollas/fisiología , Presión Osmótica , Filogenia , Epidermis de la Planta/genética , Epidermis de la Planta/metabolismo , Hojas de la Planta/metabolismo , Hojas de la Planta/fisiología , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/efectos de los fármacos , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/fisiología , Plantas Tolerantes a la Sal/efectos de los fármacos , Plantas Tolerantes a la Sal/fisiología , Semillas/efectos de los fármacos , Semillas/fisiología , Cloruro de Sodio/farmacología , Estrés Fisiológico , Activación Transcripcional , Levaduras/genética , Levaduras/metabolismoRESUMEN
UNLABELLED: NAC proteins are plant-specific transcription factors that play essential roles in stress responses. However, only little information regarding stress-related NAC genes is available in maize. In this study, a maize NAC gene, ZmSNAC1, was cloned and functionally characterized. Expression analysis revealed that ZmSNAC1 was strongly induced by low temperature, high-salinity, drought stress, and abscisic acid (ABA) treatment, but downregulated by salicylic acid treatment. Subcellular localization experiments in Arabidopsis protoplast cells indicated that ZmSNAC1 was localized in the nucleus. Transactivation assays demonstrated that ZmSNAC1 functioned as a transcriptional activator. Overexpression of ZmSNAC1 in Arabidopsis led to hypersensitivity to ABA and osmotic stress at the germination stage, but enhanced tolerance to dehydration compared to wild-type seedlings. These results suggest that ZmSNAC1 functions as a stress-responsive transcription factor in positive modulation of abiotic stress tolerance, and may have applications in the engineering of drought-tolerant crops. KEY MESSAGE: ZmSNAC1 functioned as a stress-responsive transcription factor in response to abiotic stresses, and might be useful for crop tolerance improvement.
Asunto(s)
Adaptación Fisiológica , Arabidopsis/genética , Arabidopsis/fisiología , Proteínas de Plantas/metabolismo , Estrés Fisiológico , Factores de Transcripción/metabolismo , Zea mays/metabolismo , Ácido Abscísico/farmacología , Adaptación Fisiológica/efectos de los fármacos , Adaptación Fisiológica/genética , Secuencia de Aminoácidos , Arabidopsis/efectos de los fármacos , Deshidratación , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Germinación/efectos de los fármacos , Germinación/genética , Datos de Secuencia Molecular , Presión Osmótica/efectos de los fármacos , Proteínas de Plantas/química , Proteínas de Plantas/genética , Plantas Modificadas Genéticamente , Transporte de Proteínas/efectos de los fármacos , Análisis de Secuencia de ADN , Estrés Fisiológico/efectos de los fármacos , Estrés Fisiológico/genética , Fracciones Subcelulares/efectos de los fármacos , Fracciones Subcelulares/metabolismo , Factores de Transcripción/química , Factores de Transcripción/genética , Activación Transcripcional/efectos de los fármacos , Activación Transcripcional/genética , Zea mays/efectos de los fármacos , Zea mays/genéticaRESUMEN
SnRK2 (sucrose non-fermenting 1-related protein kinases 2) represents a unique family of protein kinase in regulating signaling transduction in plants. Although the regulatory mechanisms of SnRK2 have been well demonstrated in Arabidopsis thaliana, their functions in maize are still unknown. In our study, we cloned an SnRK2 gene from maize, ZmSAPK8, which encoded a putative homolog of the rice SAPK8 protein. ZmSAPK8 had two copies in the maize genome and harbored eight introns in its coding region. We demonstrated that ZmSAPK8 expressed differentially in various organs of maize plants and was up-regulated by high-salinity and drought treatment. A green fluorescent protein (GFP)-tagged ZmSAPK8 showed subcellular localization in the cell membrane, cytoplasm and nucleus. In vitro kinase assays indicated that ZmSAPK8 preferred Mn(2+) to Mg(2+) as cofactor for phosphorylation, and Ser-182 and Thr-183 in activation loop was important for its activity. Heterologous overexpression of ZmSAPK8 in Arabidopsis could significantly strengthen tolerance to salt stress. Under salt treatment, ZmSAPK8-overexpressed transgenic plants exhibited higher germination rate and proline content, low electrolyte leakage and higher survival rate than wild type. Further analysis indicated that transgenic plants showed increased transcription of the stress-related genes, RD29A, RD29B, RAB18, ABI1, DREB2A and P5CS1, under high-salinity conditions. The results demonstrated that ZmSAPK8 was involved in diverse stress signal transduction. Moreover, no obvious adverse effects on growth and development in the ZmSAPK8-overexpressed transgenic plants implied that ZmSAPK8 was potentially useful in transgenic breeding to improve salt tolerance in crops.
Asunto(s)
Arabidopsis/genética , Proteínas Serina-Treonina Quinasas/genética , Tolerancia a la Sal , Zea mays/genética , Secuencia de Aminoácidos , Arabidopsis/efectos de los fármacos , Arabidopsis/metabolismo , Arabidopsis/fisiología , Clonación Molecular , ADN Complementario/genética , Electrólitos/metabolismo , Activación Enzimática , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Germinación , Manganeso/metabolismo , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Fosforilación , Filogenia , Plantas Modificadas Genéticamente/efectos de los fármacos , Plantas Modificadas Genéticamente/genética , Plantas Modificadas Genéticamente/metabolismo , Plantas Modificadas Genéticamente/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Transducción de Señal , Cloruro de Sodio/farmacología , Estrés Fisiológico , Transcripción Genética , Regulación hacia Arriba , Zea mays/efectos de los fármacos , Zea mays/metabolismoRESUMEN
Southern leaf blight (SLB) and northern leaf blight (NLB) are the two major foliar diseases limiting maize production worldwide. Upon previous study with the nested association mapping (NAM) population, which consist of 5,000 recombinant inbred lines from 25 parents crossed with B73, we expanded the phenotyping environments from the United States (US) to China, and increased the marker densities from 1106 to 7386 SNPs for linkage mapping, and from 1.6 to 28.5 million markers for association mapping. We identified 49 SLB and 48 NLB resistance-related unique QTLs in linkage mapping, and multiple loci in association mapping with candidate genes involved in known plant disease-resistance pathways. Furthermore, an independent natural population with 282 diversified inbred lines were sequenced for four candidate genes selected based on their biological functions. Three of them demonstrated significant associations with disease resistance. These findings provided valuable resources for further implementations to develop varieties with superior resistance for NLB and SLB.
Asunto(s)
Resistencia a la Enfermedad/genética , Ligamiento Genético , Enfermedades de las Plantas/genética , Sitios de Carácter Cuantitativo , Zea mays/genética , China , Mapeo Cromosómico/métodos , Cromosomas de las Plantas , Estudio de Asociación del Genoma Completo/métodos , Genotipo , Polimorfismo de Nucleótido Simple , Estados UnidosRESUMEN
Maize female organs are sensitive to drought stress, leading to reproductive failure and yield reduction. In the present study gene expression profiles of ears and silks of maize at the flowering stage under drought stress were investigated. From 1920 white positive clones of a forward suppression subtractive hybridization (SSH) library, 1439 available sequences of expression sequence tags (ESTs) were obtained, resulting in 361 unique ESTs after assembling. Data analysis showed that 218 of the unique ESTs had significant protein homology by BLASTX in UNIPROT database. Totally 99 uniESTs were found in TIGR maize gene indices and nr database by BLASTN, while 44 uniESTs were not found to have homologous nucleic acid sequences and putatively classified as "maize-specific" uniESTs. The 218 cDNAs with significant protein homology were sorted into 13 groups according to the functional categories of the Arabidopsis proteins. Among those genes, the genes associated with the metabolisms were the largest group (account for 27%), and the genes related to protein synthesis, protein fate, transcription, cell cycle and DNA processing accounted for 16, 10, 10 and 9%, respectively. After analysis of macroarray data and real-time quantitative polymerase chain reaction (PCR), it was found that 160 of the 218 homologous protein uniESTs were up-regulated genes in the ears, 129 in the silks, and 125 in both of the tissues. The present work provided a valuable starting point for further elucidation of the roles played by these genes/gene products in drought tolerance in maize.
Asunto(s)
Desastres , Copas de Floración/genética , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Zea mays/genética , Clonación Molecular , Perfilación de la Expresión Génica , Biblioteca de Genes , Análisis de Secuencia por Matrices de OligonucleótidosRESUMEN
Head smut, caused by the fungus Sphacelotheca reiliana (Kühn) Clint, is a devastating threat to maize production. In this study, QTL mapping of head smut resistance was performed using a recombinant inbred line (RIL) population from a cross between a resistant line "QI319" and a susceptible line "Huangzaosi" (HZS) with a genetic map constructed from genotyping-by-sequencing (GBS) data and composed of 1638 bin markers. Two head smut resistance QTL were identified, located on Chromosome 2 (q2.09HR) and Chromosome 5 (q5.03HR), q2.09HR is co-localized with a previously reported QTL for head smut resistance, and the effect of q5.03HR has been validated in backcross populations. It was also observed that pyramiding the resistant alleles of both QTL enhanced the level of resistance to head smut. A genome-wide association study (GWAS) using 277 diverse inbred lines was processed to validate the mapped QTL and to identify additional head smut resistance associations. A total of 58 associated SNPs were detected, which were distributed in 31 independent regions. SNPs with significant association to head smut resistance were detected within the q2.09HR and q5.03HR regions, confirming the linkage mapping results. It was also observed that both additive and epistastic effects determine the genetic architecture of head smut resistance in maize. As shown in this study, the combined strategy of linkage mapping and association analysis is a powerful approach in QTL dissection for disease resistance in maize.
Asunto(s)
Enfermedades de las Plantas/genética , Sitios de Carácter Cuantitativo , Zea mays/genética , Zea mays/microbiología , Mapeo Cromosómico , Cromosomas de las Plantas , Resistencia a la Enfermedad/genética , Estudio de Asociación del Genoma Completo , Técnicas de Genotipaje/métodos , Fitomejoramiento , Enfermedades de las Plantas/microbiología , Reproducibilidad de los Resultados , Ustilaginales/patogenicidadRESUMEN
Plasma membrane protein 3 (PMP3), a class of small hydrophobic polypeptides with high sequence similarity, is responsible for salt, drought, cold, and abscisic acid. These small hydrophobic ploypeptides play important roles in maintenance of ion homeostasis. In this study, eight ZmPMP3 genes were cloned from maize and responsive to salt, drought, cold and abscisic acid. The eight ZmPMP3s were membrane proteins and their sequences in trans-membrane regions were highly conserved. Phylogenetic analysis showed that they were categorized into three groups. All members of group II were responsive to ABA. Functional complementation showed that with the exception of ZmPMP3-6, all were capable of maintaining membrane potential, which in turn allows for regulation of intracellular ion homeostasis. This process was independent of the presence of Ca(2+). Lastly, over-expression of ZmPMP3-1 enhanced growth of transgenic Arabidopsis under salt condition. Through expression analysis of deduced downstream genes in transgenic plants, expression levels of three ion transporter genes and four important antioxidant genes in ROS scavenging system were increased significantly in transgenic plants during salt stress. This tolerance was likely achieved through diminishing oxidative stress due to the possibility of ZmPMP3-1's involvement in regulation of ion homeostasis, and suggests that the modulation of these conserved small hydrophobic polypeptides could be an effective way to improve salt tolerance in plants.