Abstract
BackgroundBiotic and abiotic stresses are the major cause of reduced growth, persistence, and yield in agriculture. Over the past decade, RNA-Sequencing and the use of transgenics with altered expression of stress related genes have been utilized to gain a better understanding of the molecular mechanisms leading to salt tolerance in a variety of species. Identification of transcription factors that, when overexpressed in plants, improve multiple stress tolerance may be valuable for crop improvement, but sometimes overexpression leads to deleterious effects during normal plant growth.ResultsBrachypodium constitutively expressing the BdbZIP26:GFP gene showed reduced stature compared to wild type plants (WT). RNA-Seq analysis comparing WT and bZIP26 transgenic plants revealed 7772 differentially expressed genes (DEGs). Of these DEGs, 987 of the DEGs were differentially expressed in all three transgenic lines. Many of these DEGs are similar to those often observed in response to abiotic and biotic stress, including signaling proteins such as kinases/phosphatases, calcium/calmodulin related proteins, oxidases/reductases, hormone production and signaling, transcription factors, as well as disease responsive proteins. Interestingly, there were many DEGs associated with protein turnover including ubiquitin-related proteins, F-Box and U-box related proteins, membrane proteins, and ribosomal synthesis proteins. Transgenic and control plants were exposed to salinity stress. Many of the DEGs between the WT and transgenic lines under control conditions were also found to be differentially expressed in WT in response to salinity stress. This suggests that the over-expression of the transcription factor is placing the plant in a state of stress, which may contribute to the plants diminished stature.ConclusionThe constitutive expression of BdbZIP26:GFP had an overall negative effect on plant growth and resulted in stunted plants compared to WT plants under control conditions, and a similar response to WT plants under salt stress conditions. The results of gene expression analysis suggest that the transgenic plants are in a constant state of stress, and that they are trying to allocate resources to survive.
Highlights
Biotic and abiotic stresses are the major cause of reduced growth, persistence, and yield in agriculture
Transgene expression analysis and phenotype of transgenic lines compared to wild type plants (WT) Plants (TR4, TR6, and TR7) from three independent transformation events were tested for the expression level of the bZIP26 compared to WT plants under control conditions
We investigate the possibility of over-expressing bZIP26 for improved stress tolerance, examine the effects of constitutively overexpressing the bZIP26 transcription factor on the plant phenotype, and compare transcriptomes in WT and bZIP26 transgenic lines under control and salinity stress conditions
Summary
Biotic and abiotic stresses are the major cause of reduced growth, persistence, and yield in agriculture. Biotic and abiotic stresses cause major losses in agricultural production due to reduced growth, persistence, and yield in crop species. Identification of viable strategies to reduce yield losses and improve stress tolerance is important for the goal of global food security. To develop these strategies, it is important to understand how plants sense and respond to stresses at the molecular level to facilitate the identification of target genes or pathways for improved stress tolerance. Transcription factors (TFs) participate in the signaling cascades, and are a key component in regulating gene expression in response to biotic and abiotic stresses and in growth and development [2, 3]. While there are about 60 different transcription factor families in plants [4], several families are more frequently associated with biotic and abiotic stress responses in plants, such as MYB (v-myb avian myeloblastosis viral oncogene homolog) [5], bHLH [6], AP2/ERF [7, 8], WRKY [9], NAC [10], and bZIP transcription factors [11,12,13]
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