Investigations on Regulation of MicroRNAs in Rice Reveal [Ca2+]cyt Signal Transduction Regulated MicroRNAs

Abstract

MicroRNAs (miRNAs) are critical components of the multidimensional regulatory networks in eukaryotic systems. Given their diverse spectrum of function, it is apparent that the transcription, processing, and activity of the miRNAs themselves, is very dynamically regulated. One of the most important and universally implicated signaling molecules is [Ca2+]cyt. It is known to regulate a plethora of developmental and metabolic processes in both plants and animals; however, its impact on the regulation of miRNA expression is relatively less explored. The current study employed a combination of internal and external calcium channel inhibitors to establishing that [Ca2+]cyt signatures actively regulate miRNA expression in rice. Involvement of [Ca2+]cyt in the regulation of miRNA expression was further confirmed by treatment with calcimycin, the calcium ionophore. Modulation of the cytosolic calcium levels was also found to regulate the drought-responsive expression as well as ABA-mediated response of miRNA genes in rice seedlings. The study further establishes the role of calmodulins and Calmodulin-binding Transcription Activators (CAMTAs) as important components of the signal transduction schema that regulates miRNA expression. Yeast one-hybrid assay established that OsCAMTA4 & 6 are involved in the transcriptional regulation of miR156a and miR167h. Thus, the study was able to establish that [Ca2+]cyt is actively involved in regulating the expression of miRNA genes both under control and stress conditions.

Maize miRNAs and their putative target genes involved in chilling stress response in 5-day old seedlings

“…Several studies noted the potential role of miR156 in regulating several CAMTA during periods of abiotic stress, but not in maize under low temperature conditions. Additionally, Kansal et al showed that calcium cytosolic levels, through CAMTA4 and CAMTA6, play a role in regulating the expression of os-miR156a and os-miR167h under drought conditions in rice and this could indicate a possibility that a similar relation also occurs in maize [ 56 ].…”

Advances in the Study of the Transcriptional Regulation Mechanism of Plant miRNAs

“…SPLs have been found to be target genes of miR156. In mulberry, six SPL transcription factors recognized the promoter of MIR172 and activated miR172 expression, revealing that SPL genes regulating the transcription of miR172 are involved in the flowering development in perennial woody plants [ 62 ]. From a study on citrus flower development, miR167a was found to be specifically expressed in the stamen filaments and anthers of pummelo [ 65 ].…”

“…The SERRATE protein can regulate the drought tolerance in apple by positively regulating the transcription of MIR399 and negatively regulating the transcriptions of MIR166 , MIR172 , and MIR319 [ 51 ]. In rice, a Calmodulin-binding Transcription Activator (OsCAMTA4) binds to the promoters of MIR156 and MIR167h to activate the expressions of two miRNAs, participating in the plant response to abiotic stress [ 62 ]. In addition to being part of the RNA-silencing complex to cleave mRNA in the cytoplasm, AGO1 also plays roles in miRNA biogenesis at the transcriptional level in the nucleus.…”

Genome Scale Pathway-Pathway Co-functional Synergistic Network (PcFSN) in Oryza Sativa

“…Genome-wide miRNA regulation has been already studied in rice. miRNA mediated gene regulatory network in roots, signal transduction, leaf senescence, vegetative and reproductive regulation are few examples [3][4][5][6]. Recently pathway centric co-expression studies are also gaining importance so that gap between gene expression and pathway perturbation can be minimised [7,8].…”