stimulate drought tolerance in alfalfa. Moderate levels of miR156 expression silence
SPL13 induce WD40–1 expression to adjust DFR (DIHYDROFLAVONOL-4REDUCTASE) expression for the biosynthesis of anthocyanin and regulate various
developmental, physiological, and biochemical processes in alfalfa leading to
improved drought resilience.
Salt stress causes both osmotic stress and ion toxicity in plants (Huang et al.
2019). Many miRNAs have been reported as potential candidates for salt stress
tolerance in plants having targets that are TFs as well as genes which function in
electron-transfer shuttles between proteins, laccase, K
+ transporter gene HAK5, and
others (Ding et al. 2009; Li et al. 2013; Wang et al. 2013; Sun et al. 2015a; Yuan
et al. 2015). In perennial creeping bentgrass (Agrostis stolonifera), overexpression of
rice osa-miR396c and subsequent downregulation of its target TF GRF provides salt
tolerance by improving water retention, enhanced chlorophyll content, cell membrane integrity, and Na
+ exclusion during high salinity exposure (Yuan et al. 2019).
Another study in bentgrass shows salt stress induced accumulation of mature
miR319 (Zhou and Luo 2014). Increased miR319 levels cause the downregulation
of targets AsPCF5, AsPCF6, AsPCF8 and the TF AsTCP14 (TEOSINTE
BRANCHED1, CYCLOIDEA, PROLIFERATING CELL NUCLEAR ANTIGEN
BINDING FACTOR) and positively contribute towards salinity tolerance in
bentgrass. Liu et al. (2020a) have shown that overexpressing osa-miR319b and
downregulating the targets positively regulate ethylene synthesis and salt tolerance
in switchgrass (Panicum virgatum). Salt stress enhances the expression of
gma-miR172 with a strong peak at 6 h (Song et al. 2011). Furthermore, transient
overexpression of gma-miR172a in soybean significantly enhances the survival rate
than that of the vector control plants (Pan et al. 2016). Detailed molecular analysis
has revealed that miR172a promotes salt tolerance mainly through cleaving the AP2/
EREBP-type TF gene SSAC1 to relieve its protein inhibition on thiamine biosynthesis gene THI1 that encodes a positive regulator of salt tolerance (Pan et al. 2016).
8.4
miRNAs-TFs: Regulating Cold Stress
Low temperature includes chilling (0–10
C) and freezing (<4
C) and is known to
impact the longevity and geographical distribution of plants (Josine et al. 2011).
Transcriptional control of the expression of cold responsive genes is well known
(Chinnusamy et al. 2010). miRNAs have also been added to the suite of cold
responsive gene regulatory networks. Many cold stress responsive miRNAs, including miR396, miR397, and miR319 have been identified in various plant species,
such as wheat, rice, Arabidopsis, tomato, and Brachypodium distachyon (Fig. 8.1
and Table 8.1) (Zhou et al. 2008; Barrera-figueroa et al. 2012; Tang et al. 2012; Cao
et al. 2014; Zhang et al. 2014b). In plants, cold stress induces a different set of
responses depending on the species. For example, during cold stress, miR172 is
induced in Brachypodium and Prunus persica (Zhang et al. 2009; Barakat et al.
2012) but is repressed in grapevine and wheat (Tang et al. 2012; Sun et al. 2015b). In
sugarcane and rice, cold stress leads to the induction of evolutionarily conserved
260
S. Rao et al.
SPL13 induce WD40–1 expression to adjust DFR (DIHYDROFLAVONOL-4REDUCTASE) expression for the biosynthesis of anthocyanin and regulate various
developmental, physiological, and biochemical processes in alfalfa leading to
improved drought resilience.
Salt stress causes both osmotic stress and ion toxicity in plants (Huang et al.
2019). Many miRNAs have been reported as potential candidates for salt stress
tolerance in plants having targets that are TFs as well as genes which function in
electron-transfer shuttles between proteins, laccase, K
+ transporter gene HAK5, and
others (Ding et al. 2009; Li et al. 2013; Wang et al. 2013; Sun et al. 2015a; Yuan
et al. 2015). In perennial creeping bentgrass (Agrostis stolonifera), overexpression of
rice osa-miR396c and subsequent downregulation of its target TF GRF provides salt
tolerance by improving water retention, enhanced chlorophyll content, cell membrane integrity, and Na
+ exclusion during high salinity exposure (Yuan et al. 2019).
Another study in bentgrass shows salt stress induced accumulation of mature
miR319 (Zhou and Luo 2014). Increased miR319 levels cause the downregulation
of targets AsPCF5, AsPCF6, AsPCF8 and the TF AsTCP14 (TEOSINTE
BRANCHED1, CYCLOIDEA, PROLIFERATING CELL NUCLEAR ANTIGEN
BINDING FACTOR) and positively contribute towards salinity tolerance in
bentgrass. Liu et al. (2020a) have shown that overexpressing osa-miR319b and
downregulating the targets positively regulate ethylene synthesis and salt tolerance
in switchgrass (Panicum virgatum). Salt stress enhances the expression of
gma-miR172 with a strong peak at 6 h (Song et al. 2011). Furthermore, transient
overexpression of gma-miR172a in soybean significantly enhances the survival rate
than that of the vector control plants (Pan et al. 2016). Detailed molecular analysis
has revealed that miR172a promotes salt tolerance mainly through cleaving the AP2/
EREBP-type TF gene SSAC1 to relieve its protein inhibition on thiamine biosynthesis gene THI1 that encodes a positive regulator of salt tolerance (Pan et al. 2016).
8.4
miRNAs-TFs: Regulating Cold Stress
Low temperature includes chilling (0–10
C) and freezing (<4
C) and is known to
impact the longevity and geographical distribution of plants (Josine et al. 2011).
Transcriptional control of the expression of cold responsive genes is well known
(Chinnusamy et al. 2010). miRNAs have also been added to the suite of cold
responsive gene regulatory networks. Many cold stress responsive miRNAs, including miR396, miR397, and miR319 have been identified in various plant species,
such as wheat, rice, Arabidopsis, tomato, and Brachypodium distachyon (Fig. 8.1
and Table 8.1) (Zhou et al. 2008; Barrera-figueroa et al. 2012; Tang et al. 2012; Cao
et al. 2014; Zhang et al. 2014b). In plants, cold stress induces a different set of
responses depending on the species. For example, during cold stress, miR172 is
induced in Brachypodium and Prunus persica (Zhang et al. 2009; Barakat et al.
2012) but is repressed in grapevine and wheat (Tang et al. 2012; Sun et al. 2015b). In
sugarcane and rice, cold stress leads to the induction of evolutionarily conserved
260
S. Rao et al.