Regulatory dynamics of molecular determinants in divergent rice varieties under the influence of nano-structured Zinc: an integrative study of OsbZIP genes and their targeting miRNAs

Zinc (Zn) is an indispensable micronutrient required in various physiological, biochemical, and molecular processes in plants. Zinc Oxide (ZnO), in its nano-structured form (nano-Zn) possesses unique physico-chemical properties that improve its absorption efficiency and exert a better impact on plants as compared to its bulk counterparts. The present study was conducted to investigate molecular response and cooperation between bZIP transcription factors (TFs) and microRNAs (miRs) in divergent rice varieties under nano-Zn imposition. Accordingly, spatio-structural annotations (gene-structures, Cis-elements, conserved motifs, evolutionary and syntenic nature) of OsbZIP TF genes were analyzed with their targeting Osa-miRs. Furthermore, the response of 30 OsbZIPs and 41 corresponding Osa-miRs were assessed between unlike (CSR-30 and PB-1) rice varieties under nano-Zn treatment. In CSR-30 rice, OsbZIP TFs generally showed reduced expression levels, with fold changes ranging from 0.95 to 0.44 (R² = 0.982). Correspondingly, their associated Osa-miRNAs exhibited increased expression, with changes ranging from 1x to 2.5x (R² = 0.947). In PB-1 rice, OsbZIP TFs generally exhibited reduced expression, with fold changes ranging from 0.85 to 0.47 (R² = 0.940). Similarly, their corresponding Osa-miRNAs also showed decreased expression, ranging from 1.05 to 0.30 fold change (R² = 0.940). Notably, distinct expressions were also identified for OsbZIP1, OsbZIP13, Osa-miR1846a, Osa-miR396e, Osa-miR11337a, and Osa-miR5801r, in CSR-30 rice. Additionaly, OsbZIP6, OsbZIP14, OsbZIP23, OsbZIP27, and OsbZIP29 exhibited distinct expression patterns, along with uneven responses of their corresponding Osa-miRNAs, suggesting multilayered combinatorial regulation in PB-1 rice. Therefore, the present study demonstrates the differential and coordinated responses of OsbZIP transcription factors gene family and Osa-miRNAs and also provides insights into key molecular determinants regulating rice growth under the influence of nano-Zn.