miR156-SPL and miR169-NF-YA Modules Regulate the Induction of Somatic Embryogenesis in Arabidopsis via LEC- and Auxin-Related Pathways

The embryogenic transition of plant somatic cells to produce somatic embryos requires extensive reprogramming of the cell transcriptome. The prominent role of transcription factors (TFs) and miRNAs in controlling somatic embryogenesis (SE) induction in plants was documented. The profiling of <i>MIRNA</i> expression in the embryogenic culture of Arabidopsis implied the contribution of the miR156 and miR169 to the embryogenic induction. In the present study, the function of miR156 and miR169 and the candidate targets, <i>SPL</i> and <i>NF-YA</i> genes, were investigated in Arabidopsis SE. The results showed that misexpression of <i>MIRNA156</i> and candidate <i>SPL</i> target genes (<i>SPL2</i>, <i>3</i>, <i>4</i>, <i>5</i>, <i>9</i>, <i>10</i>, <i>11</i>, <i>13</i>, <i>15</i>) negatively affected the embryogenic potential of transgenic explants, suggesting that specific fine-tuning of the miR156 and target genes expression levels seems essential for efficient SE induction. The results revealed that <i>SPL11</i> under the control of miR156 might contribute to SE induction by regulating the master regulators of SE, the <i>LEC</i> (<i>LEAFY COTYLEDON</i>) genes (<i>LEC1</i>, <i>LEC2</i>, <i>FUS3</i>). Moreover, the role of miR169 and its candidate <i>NF-YA</i> targets in SE induction was demonstrated. The results showed that several miR169 targets, including <i>NF-YA1</i>, <i>3</i>, <i>5</i>, <i>8</i>, and <i>10</i>, positively regulated SE. We found, that miR169 via <i>NF-YA5</i> seems to modulate the expression of a master SE regulator <i>LEC1/NF-YA</i> and other auxin-related genes: <i>YUCCA</i> (<i>YUC4</i>, <i>10</i>) and <i>PIN1</i> in SE induction. The study provided new insights into miR156-<i>SPL</i> and miR169-<i>NF-YA</i> functions in the auxin-related and LEC-controlled regulatory network of SE.