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Biology and Biotechnology of Environmental Stress Tolerance in Plants, Volume 3

The role of miRNA-based gene control under low-temperature stress has

been proven in numerous research works. Different functional investigations

have sought to uncover miRNA-target interactions as well as the relevance

of numerous miRNAs in cold-stress modulation. Sunkar & Zhu (2004) were

the first to show that miRNAs have a role in the modulation of cold stress.

In rice 18 COR microRNAs have been identified under low-temperature

stress at 4°C such miRNAs act as predominant regulators of plant responses

to low-temperature stress (Lv et al., 2010). At the onset of the productive

phase in the rice plant, there is a sharp expression of the COR miR812q is

comprised of unique sequences and is derived from the sequence-diverged

region. Cold stress significantly elevates the expression of miR812q, which

down-regulates CIPK10. The Ser/Thr protein kinase domain of CIPK (calci­

neurin B-like (CBL) protein-interacting protein kinase) proteins is activated

by interacting with CBL, which includes four EF-hands for Ca²⁺ binding.

Under cold stress, miR812q may be required to alter CBL-CIPK signaling

(Jeong & Green, 2013). In tea (Camellia sinensis), under cold stress 31

miRNAs are upregulated and while 43 miRNAs get downregulated. Simi­

larly, increased expression was shown by 192 miRNAs and 205 miRNAs

revealed a decreased expression in wild tomato (Solanum habrochaites)

(Cao et al., 2014).

12.2.2.2 HEAT STRESS

Increased occurrences of heatwaves and rising global temperatures influence

crop productivity and world food production severely. As global warming

progresses, heat stress (HS) seems to be a more serious food security issue.

Therefore, heat stress response and its transcriptional network have been

studied thoroughly (Ohama et al., 2017). The principal transcriptional regu­

lators in heat stress response (HSR) are heat shock transcription factor A1s

(HsfA1s). The complexity of heat stress response is decided by the multilevel

regulation of HsfA1s. HsfA1s are partially regulated by phosphorylation

or dephosphorylation, SUMOylation, and protein-protein interaction. Heat

Stress Response genes get activated by some heat-induced TFs, e.g., dehy­

dration responsive element binding protein 2A (DREB2A), multiprotein

bridging factor 1C (MBF1c), HsfA2, Hsf7s, and HsfBS. It is predicted that the

expression of such heat-induced TFs is directly regulated by HsfA1s (Ohama

et al., 2017). Histone dynamics and the RdDM route are included in HSR

(Lämke et al., 2016; Olga et al., 2013; Yang et al., 2018). Heat shock proteins