Abstract
BackgroundStress acclimation is an effective mechanism that plants acquired for adaption to dynamic environment. Even though generally considered to be sensitive to low temperature, Cassava, a major tropical crop, can be tolerant to much lower temperature after chilling acclimation. Improvement to chilling resistance could be beneficial to breeding. However, the underlying mechanism and the effects of chilling acclimation on chilling tolerance remain largely unexplored.ResultsIn order to understand the mechanism of chilling acclimation, we profiled and analyzed the transcriptome and microRNAome of Cassava, using high-throughput deep sequencing, across the normal condition, a moderate chilling stress (14°C), a harsh stress (4°C) after chilling acclimation (14°C), and a chilling shock from 24°C to 4°C. The results revealed that moderate stress and chilling shock triggered comparable degrees of transcriptional perturbation, and more importantly, about two thirds of differentially expressed genes reversed their expression from up-regulation to down-regulation or vice versa in response to hash stress after experiencing moderate stress. In addition, microRNAs played important roles in the process of this massive genetic circuitry rewiring. Furthermore, function analysis revealed that chilling acclimation helped the plant develop immunity to further harsh stress by exclusively inducing genes with function for nutrient reservation therefore providing protection, whereas chilling shock induced genes with function for viral reproduction therefore causing damage.ConclusionsOur study revealed, for the first time, the molecular basis of chilling acclimation, and showed potential regulation role of microRNA in chilling response and acclimation in Euphorbia.
Highlights
Stress acclimation is an effective mechanism that plants acquired for adaption to dynamic environment
By analyzing more than 35.3 million sequencing reads from 4 mRNA libraries and 25.6 million reads from 4 small noncoding RNAs (sncRNAs) libraries, we identified differentially expressed mRNA and miRNA genes, from which we further identified and analyzed mRNA and miRNA genes that are critical to chilling acclimation
The profiling experiments were carried out under three chilling stress treatments: 1) gradual chilling acclimation (CA) where plants grown in the normal condition of 24°C were stressed to 14°C; 2) chilling stress after chilling acclimation (CCA) where plants after 5 days of the CA treatment were transferred further from 14°C to 4°C; and 3) chilling shock (CS) where plants were experienced a dramatic temperature drop from 24°C to 4°C
Summary
Stress acclimation is an effective mechanism that plants acquired for adaption to dynamic environment. Even though generally considered to be sensitive to low temperature, Cassava, a major tropical crop, can be tolerant to much lower temperature after chilling acclimation. The underlying mechanism and the effects of chilling acclimation on chilling tolerance remain largely unexplored. Chilling acclimation is a favorable trait that is critical for plant growth, reproduction and survival. Chilling responses of tropical plants has been documented: an oxidative signaling regulatory network triggers an early response to chilling stress in Japonica rice [7], and exogenous ABA can induce freezing tolerance in chilling sensitive rice seedlings [8]. A chloroplast-targeted protein complex stabilization related DnaJ protein contributes to maintenance of photosystem II under chilling stress in tomato [11]
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