Abstract
Plants are exposed every day to multiple environmental cues, and tight transcriptome reprogramming is necessary to control the balance between responses to stress and processes of plant growth. In this context, the silencing phenomena mediated by small RNAs can drive transcriptional and epigenetic regulatory modifications, in turn shaping plant development and adaptation to the surrounding environment. Mounting experimental evidence has recently pointed to small noncoding RNAs as fundamental players in molecular signalling cascades activated upon exposure to abiotic and biotic stresses. Although, in the last decade, studies on stress responsive small RNAs increased significantly in many plant species, the physiological responses triggered by these molecules in the presence of environmental stresses need to be further explored. It is noteworthy that small RNAs can move either cell-to-cell or systemically, thus acting as mobile silencing effectors within the plant. This aspect has great importance when physiological changes, as well as epigenetic regulatory marks, are inspected in light of plant environmental adaptation. In this review, we provide an overview of the categories of mobile small RNAs in plants, particularly focusing on the biological implications of non-cell autonomous RNA silencing in the stress adaptive response and epigenetic modifications.
Highlights
The way a plant responds to environmental stimuli during its lifetime is guided by an intricate and coordinated array of physiological and biochemical events [1,2]
SncRNAs are classified into two main classes: short-interfering RNAs and microRNAs
This is the case with the long non-coding RNAs (lncRNAs) IPS1 (Induced by Phosphate Starvation 1), which competes with PHO2 to bind miR399 [104]
Summary
The way a plant responds to environmental stimuli during its lifetime is guided by an intricate and coordinated array of physiological and biochemical events [1,2]. Depending on their size and recipient tissues, diverse types of small molecules can be transported through PD pores, such as ions, metabolites, hormones, Short-distance delivery of RNAs occurs in a cell-to-cell manner and, essentially, via plasmodesmata (PD), which establish cytosolic continuity between adjacent cells (i.e., symplastic movement) (Figure 1). Depending on their size and recipient tissues, diverse types of small molecules can be transported through PD pores, such as ions, metabolites, hormones, proteins, mRNAs and sncRNAs. the PD act as dynamic channels that can undergo structural and functional changes induced by specific plant developmental stages or environmental stressors. Since viroids must use only host proteins for their translocation [49], they represent an ideal system to gain insights into the intercellular transport of endogenous RNA molecules
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