roles of TF:miRNA:target modules in different abiotic stress responses in various
plant species including model and crop plants. This information will aid in
understanding the mechanisms of action and interactions between these
regulators in plant growth and development under normal as well as environmental stress conditions and pave the path to engineer more resilient plants in the
future.
Keywords
Transcription factors · microRNA · Abiotic stress · Heat · Cold · Salinity and
heavy metal stress · Homeostasis
8.1
Introduction
Environmental factors that negatively affect plant growth and development are
collectively recognized as various forms of abiotic stress. Plants are constantly
exposed to adverse conditions, such as high temperature, drought, high salinity,
cold, heavy metals, and nutrient deficiency. These factors limit the geographical
distribution of plants and also affect crop yield. Being sessile in nature, plants have
evolved sophisticated and robust mechanisms to cope with the myriad stresses they
encounter (Zhang 2015; Zhu 2016; Bielach et al. 2017; Nolan et al. 2017; Zarattini
and Forlani 2017). At the forefront of these are regulatory responses to maintain
physiological homeostasis through specific and well-defined reprogramming of the
transcriptional and post-transcriptional activities by transcription factors (TFs) and a
class of small 20–22 nucleotides long non-coding endogenous RNAs called
microRNAs (miRNAs), respectively.
Transcription factors are the key regulators of gene expression belonging to
multigene families in plants (Salih et al. 2016). TFs act by recognizing the ciselements in the promoter region of different stress responsive genes including
various miRNAs (Yant et al. 2010; Wang and Perry 2013; Biłas et al. 2016). TF
genes are regulated at both transcriptional and post-transcriptional levels in plants
(Mitsuda and Ohme-Takagi 2009; Payne and Wagner 2015; Chen et al. 2017;
Hernando et al. 2017). MicroRNAs act via direct mRNA cleavage, translational
repression, and DNA methylation of its targets based on sequence complementarity.
MIRNA genes are first transcribed into primary miRNAs (pri-miRNAs) by RNA
polymerase II (Pol II) (Xie et al. 2005; Kim et al. 2011). Besides the TATA box core
promoter element, MIR promoters are enriched in various cis-regulatory elements
that regulate the transcription of MIRs in different developmental stages and/or
varied environmental cues by recruiting different TFs. In contrast to animals, only
a small portion of genes have been validated as true targets of plant miRNAs, i.e.,
less than 1% of protein coding genes (Addo-Quaye et al. 2009; Li et al. 2010).
However, the overall impact of miRNA-mediated gene regulation in plants cannot
be underestimated as most of the target genes are TFs (Jones-Rhoades et al. 2006)
that regulate several developmental and plant stress responses. The identification and
252
S. Rao et al.
plant species including model and crop plants. This information will aid in
understanding the mechanisms of action and interactions between these
regulators in plant growth and development under normal as well as environmental stress conditions and pave the path to engineer more resilient plants in the
future.
Keywords
Transcription factors · microRNA · Abiotic stress · Heat · Cold · Salinity and
heavy metal stress · Homeostasis
8.1
Introduction
Environmental factors that negatively affect plant growth and development are
collectively recognized as various forms of abiotic stress. Plants are constantly
exposed to adverse conditions, such as high temperature, drought, high salinity,
cold, heavy metals, and nutrient deficiency. These factors limit the geographical
distribution of plants and also affect crop yield. Being sessile in nature, plants have
evolved sophisticated and robust mechanisms to cope with the myriad stresses they
encounter (Zhang 2015; Zhu 2016; Bielach et al. 2017; Nolan et al. 2017; Zarattini
and Forlani 2017). At the forefront of these are regulatory responses to maintain
physiological homeostasis through specific and well-defined reprogramming of the
transcriptional and post-transcriptional activities by transcription factors (TFs) and a
class of small 20–22 nucleotides long non-coding endogenous RNAs called
microRNAs (miRNAs), respectively.
Transcription factors are the key regulators of gene expression belonging to
multigene families in plants (Salih et al. 2016). TFs act by recognizing the ciselements in the promoter region of different stress responsive genes including
various miRNAs (Yant et al. 2010; Wang and Perry 2013; Biłas et al. 2016). TF
genes are regulated at both transcriptional and post-transcriptional levels in plants
(Mitsuda and Ohme-Takagi 2009; Payne and Wagner 2015; Chen et al. 2017;
Hernando et al. 2017). MicroRNAs act via direct mRNA cleavage, translational
repression, and DNA methylation of its targets based on sequence complementarity.
MIRNA genes are first transcribed into primary miRNAs (pri-miRNAs) by RNA
polymerase II (Pol II) (Xie et al. 2005; Kim et al. 2011). Besides the TATA box core
promoter element, MIR promoters are enriched in various cis-regulatory elements
that regulate the transcription of MIRs in different developmental stages and/or
varied environmental cues by recruiting different TFs. In contrast to animals, only
a small portion of genes have been validated as true targets of plant miRNAs, i.e.,
less than 1% of protein coding genes (Addo-Quaye et al. 2009; Li et al. 2010).
However, the overall impact of miRNA-mediated gene regulation in plants cannot
be underestimated as most of the target genes are TFs (Jones-Rhoades et al. 2006)
that regulate several developmental and plant stress responses. The identification and
252
S. Rao et al.