RESUMEN
Peanut (Arachis hypogaea L.) produces flowers aerially, but the fruit develops underground. This process is mediated by the gynophore, which always grows vertically downwards. The genetic basis underlying gravitropic bending of gynophores is not well understood. To identify genes related to gynophore gravitropism, gene expression profiles of gynophores cultured in vitro with tip pointing upward (gravitropic stimulation sample) and downward (control) at both 6 and 12h were compared through a high-density peanut microarray. After gravitropic stimulation, there were 174 differentially expressed genes, including 91 upregulated and 83 downregulated genes at 6h, and 491 differentially expressed genes including 129 upregulated and 362 downregulated genes at 12h. The differentially expressed genes identified were assigned to 24 functional categories. Twenty pathways including carbon fixation, aminoacyl-tRNA biosynthesis, pentose phosphate pathway, starch and sucrose metabolism were identified. The quantitative real-time PCR analysis was performed for validation of microarray results. Our study paves the way to better understand the molecular mechanisms underlying the peanut gynophore gravitropism.
RESUMEN
Pre-harvest aflatoxin contamination caused by Aspergillus favus is a major concern in peanut. However, little is known about the resistance mechanism, so the incorporation of resistance into cultivars with commercially-acceptable genetic background has been slowed. To identify resistance-associated genes potentially underlying the resistance mechanism, we compared transcriptome profiles in resistant and susceptible peanut genotypes under three different treatments: well watered, drought stress and both A. flavus and drought stress using a customised NimbleGen microarray representing 36158 unigenes. Results showed that the profile of differentially expressed genes (DEGs) displayed a similar pattern of distribution among the functional classes between resistant and susceptible peanuts in response to drought stress. Under A. flavus infection with drought stress, a total of 490 unigenes involved in 26 pathways were differentially expressed in the resistant genotype YJ1 uniquely responding to A. flavus infection, in which 96 DEGs were related to eight pathways: oxidation reduction, proteolysis metabolism, coenzyme A biosynthesis, defence response, signalling, oligopeptide transport, transmembrane transport and carbohydrate biosynthesis/metabolism. Pathway analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that eight networks were significantly associated with resistance to A. flavus infection in resistant genotype YJ1 compared with susceptible Yueyou7. To validate microarray analysis, 15 genes were randomly selected for real-time RT-PCR analysis. The results provided in this study may enhance our understanding of the pre-harvest peanut-A. flavus interaction and facilitate to develop aflatoxin resistant peanut lines in future breeding programs.
RESUMEN
Peanut (Arachis hypogaea L.) is one of the most important oil-bearing crops in the world. The gravitropic response of peanut gynophores plays an essential role in peanut reproductive development. In this study, we developed an in vitro culture system and applied it to the study of peanut gynophore gravitropism. By comparing the proteomes of gynophores grown in vitro with the tip pointing upward (gravity stimulation sample) and downward (natural growth control) at 6h and 12h, we observed 42 and 39 with significantly altered expression pattern at 6 and 12h, respectively. Out of these proteins, 13 proteins showed same expression profiling at both 6h and 12h. They were identified by MALDI-TOF/TOF and further characterized with quantitative real time RT-PCR. Among the 13 identified proteins, two were identified as class III acidic endochitinases, two were identified as Kunitz trypsin protease inhibitors, and the remaining proteins were identified as pathogenesis-related class 10 protein, Ara h 8 allergen isoform 3, voltage-dependent anion channel, gamma carbonic anhydrase 1, germin-like protein subfamily 3 member 3 precursor, chloride channel, glycine-rich RNA-binding protein and gibberellin receptor GID1. Real time RT-PCR analysis revealed that transcriptional regulation is consistent with expression at the protein level for class III acidic endochitinase, Kunitz trypsin protease inhibitor, chloride channel and pathogenesis-related class 10 protein, while the expression of the other 7 proteins might be regulated at post-transcriptional levels. This study identified several potential gravitropic response proteins in peanut gynophores and helps to understand early gravitropic responses in peanut gynophores. BIOLOGICAL SIGNIFICANCE: The gravitropic response of the peanut gynophores plays an essential role in peanut production. However, the molecular mechanism responsible for gravitropic responses in the peanut gynophores has not been explored yet. The result generated in this study may provide in vitro culture system for gravitropism study of plant gravitropic response and novel insights into the proteome-level response and give a more comprehensive understanding of early gravitropic response in peanut gynophores. This article is part of a Special Issue entitled: Translational Plant Proteomics.