Elevated CO modulates miRNA expression level differentially in Arabidopsis thaliana populations originated at different elevations of Indian West Himalayas.

Plants response towards increasing atmospheric [CO] have predominantly been investigated in great details in context to morpho-physiology and gene regulation. While miRNAs are known to play critical roles in stress responses, the impact of elevated CO₂ on miRNA regulation especially in plant populations evolved under different climatic conditions remains unexplored. Plant populations evolved at different climatic conditions may respond differently towards specific stress. Here, we investigated the expression pattern of miRNAs in the two Indian Arabidopsis thaliana populations evolved at very high (3400 m amsl) and low elevation (700 m amsl) zones of west Himalayas in response to elevated [CO]. A total of 23 and 14 miRNAs were differentially expressed between the populations under ambient and elevated [CO] conditions, respectively. On the other hand, 15 and eight miRNAs were differentially expressed in the high and in the low elevation population when compared between ambient and elevated [CO] condition. The target genes of these miRNAs are involved in various biological processes. Our results also suggest activation of miR390 induced cascade of auxin signalling pathway under elevated [CO] in both the populations. Under elevated [CO] the expression of miR390 is decreased leading to higher level of its target ARFs. Overall, our results demonstrate elevated [CO] induced population specific differential modulation of miRNAs expression and auxin signalling pathway regulation by miR390 in the low and elevation populations of Arabidopsis thaliana. The findings suggest that elevated CO₂ influences small RNA-regulated plant growth and development, offering potential strategies for climate-resilient crop management.