Table 2.

Functional studies involving miRNA156, miR166, and miR319. The target transcription factors of the miRNAs, effects on the expression of downstream or cold stress-responsive genes regulated by the transcription factors are provided. The observed phenotypic effects of the miRNA regulation under cold stress are also included.

miRNA	Target transcription factors	Observed effects on downstream or other cold stress-responsive genes	Phenotypic observation	References
miR156 (OsmiR156)	SPL3	Suppression of OsWRKY71 leading to enhanced expression of OsMYB2 and OsMYB3R-2.	Enhancement in cell viability, growth rate and reduction in ion leakage under cold stress in Arabidopsis, pine, and rice over-expressing rice OsmiRNA156	Zhou and Tang, 2019
miR156k (Osmi156k)	SPL3, SPL14 and SPL17	Suppression of proline synthase and ROS scavenger genes	Seedlings’ growth inhibition at the very early stage, lower survival rates, lower ROS scavengers, reduction in chlorophyll and proline contents in rice over-expressing OsmiR156k	Cui et al., 2015
miR166 and miR319	HD-ZIP III and TCP4-like	N/A	Downregulated expression of miR166 and miR319 in roots under cold stress led to increase expression of HD-ZIP III and TCP4-like that potentially improve cell wall thickness and strength in the cold-tolerant cultivar.	Zeng et al., 2018
miR319 (Osa-miR319b)	TCP21, PCF5 and PCF6	Higher expression of CBF/DREB1	Increase in proline, plant survival rate and ROS scavenging capacity under cold stress of transgenic rice over-expressing Osa-miR319b	Wang et al., 2014b
miRNA319 (sha-miR319d)	GAMYB-like1	Promote expression of genes involved in chilling (CBF1 and MYB83), heat stress response (HSFA1a, HSFA1b and HSP90), and ROS signaling (ZAT12 and ZAT10) and scavenging (SOD CAT)	Lower relative electrolyte leakage and malondialdehyde concentration, reduced O2− generation and H2O2 concentration and higher chlorophyll contents and Fv/Fm values in cultivated tomato cultivar over-expressing sha-miR319d from wild tomato	Shi et al., 2019