Project description:Background: Cassava is an important tropical root crop adapted to a wide range of environmental stimuli such as drought and acid soils. Nevertheless, it is an extremely cold-sensitive tropical species. Thus far, there is limited information about gene regulation and signaling pathways related to the cold stress response in cassava. The development of microarray technology has accelerated the study of global transcription profiling under certain conditions. Results: A 60-mer oligonucleotide 4X44K Agilent microarray representing 20,840 genes was used to perform transcriptome profiling in cassava apical shoots subjected to cold at 7M-BM-0C for 0 h, 4 h, and 9 h. A total of 508 transcripts were identified as early cold-responsive genes in which 319 sequences had descriptions when they were aligned with Arabidopsis proteins. Gene ontology (GO) annotation analysis identified many interesting categories including M-bM-^@M-^XResponse to abiotic and biotic stimulusM-bM-^@M-^Y, M-bM-^@M-^XResponse to stressM-bM-^@M-^Y, M-bM-^@M-^XTranscription factor activityM-bM-^@M-^Y, and M-bM-^@M-^XChloroplastM-bM-^@M-^Y. Various stress-associated genes comprising signal transduction components (e.g., MAP kinase 4), transcription factors (TFs; e.g., RAP2.11), and ROS scavenging enzymes (e.g., catalase 2), as well as photosynthesis-related genes (e.g., PSAL), were found. Seventeen major TF families were also identified as being involved in the early response to cold stress (e.g., AP2-EREBP). Meanwhile, KEGG pathway analysis uncovered many important pathways, including M-bM-^@M-^XPlant hormone signal transductionM-bM-^@M-^Y, M-bM-^@M-^XStarch and sucrose metabolismM-bM-^@M-^Y, and M-bM-^@M-^XPlant-pathogen interactionM-bM-^@M-^Y. Furthermore, the expression changes of 18 genes under cold and other abiotic stresses conditions were validated by real-time RT-PCR. As a response to cold stress in cassava, an increase in the ROS scavenging enzyme activities of catalase and superoxide dismutases and the accumulation of total soluble sugars were also detected. Importantly, most of the tested stress-responsive genes were primarily expressed in mature leaves, stem cambia, and fibrous roots rather than apical buds and young leaves. Conclusions: The dynamic expression changes reflect the integrative controlling and transcriptome regulation of the networks in the early cold stress response of cassava. The biological processes involved in the signal perception and physiological response might shed light on the molecular mechanisms related to cold tolerance in tropical plants and provide useful candidate genes for genetic improvement. Apical shoots subjected to cold at 7M-BM-0C for 0 h, 4 h, and 9 h were collected for RNA extractions from three independent healthy 3-month-old cassava (cultivar TMS60444) plants in the greenhouse.

Project description:External application of acetic acid has been recently reported to enhance the survival to drought in plants such as Arabidopsis, rapeseed, maize, rice and wheat, but the effects of acetic acid application on increased drought tolerance in woody plants such as a tropical crop “cassava” remain elusive. A molecular understanding of acetic acid-induced drought avoidance in cassava will contribute to the development of technology that can be used to enhance drought tolerance without resorting to transgenic technology or advancements in cassava cultivation. In the present study, morphological, physiological and molecular responses to drought were analyzed in cassava after the treatment with acetic acid. Results indicated that the acetic acid-treated cassava plants had a higher level of drought avoidance than water-treated, control plants. Specifically, higher leaf relative water content, and chlorophyll and carotenoid levels were observed as soils dried out during the drought treatment. Leaf temperatures in acetic acid-treated cassava plants were higher relative to leaves on plants pretreated with water and the increase of ABA content was observed in leaves of acetic acid-treated plants, suggesting that stomatal conductance and the transpiration rate in leaves of acetic acid-treated plants decreased to maintain relative water contents and avoid drought. Transcriptome analysis revealed that the acetic acid treatment increased the expression of ABA signaling-related genes, such as OPEN STOMATA 1　(OST1) and protein phosphatase 2C; as well as drought response and tolerance-related genes, such as outer membrane tryptophan-rich sensory protein (TSPO), and heat shock proteins. Collectively, the external application of acetic acid enhances drought avoidance in cassava through the upregulation of ABA signaling pathway genes and several stress response- and tolerance-related genes. These data support the idea that adjustments of the acetic acid application to plants is useful to enhance drought tolerance in order to minimize the growth inhibition in the agricultural field.

Project description:Background: Cassava is an important tropical root crop adapted to a wide range of environmental stimuli such as drought and acid soils. Nevertheless, it is an extremely cold-sensitive tropical species. Thus far, there is limited information about gene regulation and signaling pathways related to the cold stress response in cassava. The development of microarray technology has accelerated the study of global transcription profiling under certain conditions. Results: A 60-mer oligonucleotide 4X44K Agilent microarray representing 20,840 genes was used to perform transcriptome profiling in cassava apical shoots subjected to cold at 7°C for 0 h, 4 h, and 9 h. A total of 508 transcripts were identified as early cold-responsive genes in which 319 sequences had descriptions when they were aligned with Arabidopsis proteins. Gene ontology (GO) annotation analysis identified many interesting categories including ‘Response to abiotic and biotic stimulus’, ‘Response to stress’, ‘Transcription factor activity’, and ‘Chloroplast’. Various stress-associated genes comprising signal transduction components (e.g., MAP kinase 4), transcription factors (TFs; e.g., RAP2.11), and ROS scavenging enzymes (e.g., catalase 2), as well as photosynthesis-related genes (e.g., PSAL), were found. Seventeen major TF families were also identified as being involved in the early response to cold stress (e.g., AP2-EREBP). Meanwhile, KEGG pathway analysis uncovered many important pathways, including ‘Plant hormone signal transduction’, ‘Starch and sucrose metabolism’, and ‘Plant-pathogen interaction’. Furthermore, the expression changes of 18 genes under cold and other abiotic stresses conditions were validated by real-time RT-PCR. As a response to cold stress in cassava, an increase in the ROS scavenging enzyme activities of catalase and superoxide dismutases and the accumulation of total soluble sugars were also detected. Importantly, most of the tested stress-responsive genes were primarily expressed in mature leaves, stem cambia, and fibrous roots rather than apical buds and young leaves. Conclusions: The dynamic expression changes reflect the integrative controlling and transcriptome regulation of the networks in the early cold stress response of cassava. The biological processes involved in the signal perception and physiological response might shed light on the molecular mechanisms related to cold tolerance in tropical plants and provide useful candidate genes for genetic improvement.

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Manihot esculenta

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