Cotton Genomics and Genetics 2016, Vol.7, No.2, 1-23
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distachyon
. Shuai et al. (2013) shown that the expression patterns and RT-qPCR results of drought-responsive
miRNAs in
Populus
were consistent and both indicating that miR159 members were up-regulated after drought
treatment. Similar kind of up regulation of miR159 under drought was also reported in legumes (Mantri et al.,
2013), finger millet (Nageshbabu et al., 2013) and in cotton (Wang et al., 2013).
Eight members of up regulated miR162 with maximum elevated expression of 15.071 folds (Supplementary Table
1) was found in water stressed KC3 leaves in this study. Similar kind of up regulation of miR162 under drought
was reported in cotton
(Wang et al., 2013) and
Brachypodium
(Bertolinia et al., 2013). Up regulation of miR162
under salt stress was has also been reported in roots of
Vigna unguiculata
(Paul et al., 2011). In cotton, Ruan et al.
(2009) have shown that miR162 target zinc finger protein and miR162 was also found to be key regulator of
dicer-like protein (DCL) that are essential for miRNA or small RNA biogenesis (Liu et al., 2009). Khraiswesh et
al. (2012)
have shown that both up regulation of miR162 in salt-shocked maize roots and down regulation of
miR162 under mechanical stress.
Totally 20 members of miR166 family was found that were both up (two members; with maximum fold change of
4.949) and down (18 members; with maximum fold change of 5.305) in Suvin under water stress
(Supplementary
Table 1). Both up regulation (in
Medicago truncatula
plants subjected to progressive water deficit; Trindade et al.,
2010) and down regulation (in
Triticum dicoccoides
in response to shock drought stress; Kantar et al., 2010) of
miR166 was reported earlier. It has shown that miR166 was chiefly expressed under abiotic stresses in cassava
and has basic-leucine zipper (bZIP) transcription factor as target (Ballén-Taborda et al., 2013) which is shown to
be involved in ABA and abiotic stress signalling in several plant species (Nicolas et al., 2014). Clear role for up
and down regulation of miR166 was not yet deciphered; hence, additional studies on miR166 under drought stress
should shed more information on precise molecular details on stress resistance mechanisms in plants.
Down regulation of 5 members of miR167 was noticed in Suvin-WS (Supplementary Table 1). Microarray
analysis showed that miR167 was up regulated by drought stress in Arabidopsis and miR167 has been reported to
play major roles in drought and ABA response in plants (Liu et al., 2008). Similar to more than 5 fold down
regulation of miR169 in KC3-WS, down regulation of miR169 has also been noticed in drought resistant, soybean
(Ni et al., 2013). It has experimentally validated that
GmNFYA3
(a gene encoding Nuclear factor Y (NF-Y), which
is a heterotrimeric transcription factor), was target gene of miR169 and demonstrated that
GmNFYA3
is a positive
regulator of plant tolerance to drought stress (Ni et al., 2013). In addition, Xu et al. (2014) evidently demonstrated
that miR169 family members might be involved in flowering time regulation under abiotic stresses in plants
including drought. Plants often flower earlier under water stress conditions and early flowering is considered as
one of the key drought resistance component traits in plants (Komashita et al., 2008). The stress-activated
transition to flowering enhances the chance of a plant population surviving under the threatening water stress.
All the four members of miR171 were up regulated in KC3-WS (Supplementary Table 1). Induced expression of
miR171 was shown in barley under dehydration stress and the identified targets for miR171 was scarecrow like 6
(SCRL6). It encodes a transcription factor that is involved in diverse plant developmental processes such as leaf or
root (Kantar et al., 2010).
Elevated up regulation of miR276 (57.625 fold; Supplementary Table 1) was found in this study in KC3-WS and
to the best of our knowledge, there is no report in plant that specifies the role of miR276 under water stress.
However, it has been reported in insects and shown to have key role in larval development and age dependent
behavioural changes (Hori et al., 2010; Kozomara and Griffiths-Jones, 2011).
Yet another miRNA family that has high level of induction in KC3-WS were two members of miR279 (maximum
of 58.068 fold changes; Supplementary Table 1). Up regulated expression of miR279 was mainly found in roots
and it is expressed at lower levels in leaves, and scarcely expressed in stems and booting panicles in the common
wild rice,
O. rufipogon
(Chen et al., 2013). However, their role in drought tolerance in plant is yet to be
determined at molecular level.
