ABSTRACT: Moderate stress acclimation provides immunity to stress by rewiring regulatory networks and inducing genes with protective functions in Cassava
Project description:Stress acclimation is an effective mechanism that plants acquired for adaption to dynamic environmental conditions. After undergoing cold acclimation, plants become more tolerant to cold stress. In order to understand the mechanism of cold acclimation, we performed a systematic, comprehensive study of cold response and acclimation in Cassava (Manihot esculenta), a staple crop and major food source in the tropical regions of the world. We profiled mRNA genes and small-RNA species, using next generation sequencing, and performed an integrative analysis of the transcriptome and microRNAome of Cassava across the normal condition, a moderate cold stress at 14M-BM-0C, a harsh stress at 4M-BM-0C after cold acclimation at 14M-BM-0C, and a cold shock from 24M-BM-0C to 4M-BM-0C. Two results from the analysis were striking. First, the moderate stress and cold shock, despite a difference of 10M-BM-0C between the two, triggered comparable degrees of perturbation to the transcriptome; in contrary, further harsh stress after cold acclimation resulted in a much smaller degree of transcriptome variation. Second and more importantly, about two thirds of the up- or down-regulated genes after moderate stress reversed their expression to down- or up-regulation, respectively, under harsh stress after cold acclimation, resulting in a genome-wide rewiring of regulatory networks. MicroRNAs, which are key post-transcriptional gene regulators, were major players in this massive rewiring of genetic circuitry. Further, a function enrichment analysis of the perturbed genes revealed that cold acclimation helped the plant to develop immunity to further harsh stress by exclusively inducing genes with functions of nutrient reservoir; in contrast, many genes with functions of viral reproduction were induced by cold shock. Our study revealed, for the first time, the molecular basis of stress acclimation in plants, and shed lights on the role of microRNA gene regulation in cold response and acclimation in Euphorbia. Three organs/tissues (folded leaf, fully expanded leaf and roots) of Cassava cultivar SC124 harvested at 6h, 24h and 5d for three cold treatments of CA, CCA and CS, for gene expression profiling at the stages of initial response, secondary response, and functional adaption to cold stresses. Total RNA of each sample was isolated individually, and then pooled with an equal amount from each sample into one for profiling. As a result, four mRNA libraries and four small-RNA libraries, corresponding to the conditions of CA, CCA, CS and NC, were constructed.
Project description:Stress acclimation is an effective mechanism that plants acquired for adaption to dynamic environmental conditions. After undergoing cold acclimation, plants become more tolerant to cold stress. In order to understand the mechanism of cold acclimation, we performed a systematic, comprehensive study of cold response and acclimation in Cassava (Manihot esculenta), a staple crop and major food source in the tropical regions of the world. We profiled mRNA genes and small-RNA species, using next generation sequencing, and performed an integrative analysis of the transcriptome and microRNAome of Cassava across the normal condition, a moderate cold stress at 14°C, a harsh stress at 4°C after cold acclimation at 14°C, and a cold shock from 24°C to 4°C. Two results from the analysis were striking. First, the moderate stress and cold shock, despite a difference of 10°C between the two, triggered comparable degrees of perturbation to the transcriptome; in contrary, further harsh stress after cold acclimation resulted in a much smaller degree of transcriptome variation. Second and more importantly, about two thirds of the up- or down-regulated genes after moderate stress reversed their expression to down- or up-regulation, respectively, under harsh stress after cold acclimation, resulting in a genome-wide rewiring of regulatory networks. MicroRNAs, which are key post-transcriptional gene regulators, were major players in this massive rewiring of genetic circuitry. Further, a function enrichment analysis of the perturbed genes revealed that cold acclimation helped the plant to develop immunity to further harsh stress by exclusively inducing genes with functions of nutrient reservoir; in contrast, many genes with functions of viral reproduction were induced by cold shock. Our study revealed, for the first time, the molecular basis of stress acclimation in plants, and shed lights on the role of microRNA gene regulation in cold response and acclimation in Euphorbia.
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:Full length long read transcript sequences were used as guides along with other multi-omics data to build gene model annotation of Cassava.
Project description:Cassava (Manihot esculenta) is one of the most important staple food crops worldwide. Its starchy tuberous roots supply over 800 million people with carbohydrates. Yet, surprisingly little is known about the processes involved in filling of those vital storage organs. A better understanding of cassava carbohydrate allocation and starch storage is key to improve storage root yield. In this work, we studied cassava morphology and phloem sap flow from source to sink using transgenic pAtSUC2::GFP plants, the phloem tracers esculin and 5(6)-carboxyfluorescein diacetate (CFDA), as well as several staining techniques. We show that cassava performs apoplasmic phloem loading in source leaves and symplasmic unloading into phloem parenchyma cells of tuberous roots. We demonstrate that vascular rays play an important role in radial transport from the phloem to xylem parenchyma cells in tuberous roots. Furthermore, enzymatic and proteomic measurements of storage root tissues confirmed high abundance and activity of enzymes involved in the sucrose synthase-mediated pathway and indicated that starch is stored most efficiently in the outer xylem layers of tuberous roots. Our findings represent a first basis for biotechnological approaches aimed at improved phloem loading and enhanced carbohydrate allocation and storage in order to increase tuberous root yield of cassava.
Project description:Small noncoding RNA (sncRNA), including microRNAs (miRNAs) and endogenous small-interfering RNAs (endo-siRNAs) are key gene regulators in eukaryotes, playing critical roles in plant development and stress tolerance. Trans-acting siRNAs (ta-siRNAs), which are secondary siRNAs triggered by miRNAs, and siRNAs from natural antisense transcripts (nat-siRNAs) are two well-studied classes of endo-siRNAs. In order to understand sncRNAsM-bM-^@M-^Y roles in plant cold response and stress acclimation, we studied miRNAs and endo-siRNAs in Cassava (Manihot esculenta), a major source of food for the world populations in tropical regions. Combining Next-Generation sequencing and computational and experimental analyses, we profiled and characterized sncRNA species and mRNA genes from the plants that experienced severe and moderate cold stresses, that underwent further severe cold stress after cold acclimation at moderate stress, and that grew under the normal condition. We also included Castor bean (Ricinus communis) to understand conservation of sncRNAs. In addition to known miRNAs, we identified dozens of novel miRNAs as well as ta-siRNA-yielding and nat-siRNA-yielding loci in Cassava and Castor bean, respectively. Among the expressed sncRNAs, many sncRNAs were differentially expressed under cold stresses. Our study provided the results on gene regulation by sncRNAs in cold acclimation of Euphorbiaceous plants and the role of sncRNA-mediated pathways affected by cold stress and stress acclimation in Cassava. Examination of small RNA populations in Cassava cultivar SC124 under the normal condition (NC), gradual cold acclimation (CA), cold shock (CS) and stress acclimation Cold stress after cold acclimation (CCA).