The Evolutionary Journey of NAC Genes in Plants

Taking a trip back in time to see how plants adapted to life on land. One key player in this story is the NAC transcription factor. NAC genes are like the conductors of an orchestra, directing how plants grow, develop, and respond to stress. We looked at plants from green algae to today's crops to understand how these genes evolved. Green algae had a few NAC genes, but as plants moved onto land, the number shot up. By the time we reached flowering plants, there was a huge increase. We found that some NAC gene groups only appeared later in evolution, like those unique to flowering plants with seeds inside fruits (eudicots) or those with a single seed (monocots). These NAC genes seemed to have an ancient role in dealing with the environment and plant growth. We found signs of this in the parts of the genes that control how and when they're turned on. These parts, called cis-elements, suggested that NAC genes help plants respond to heat, cold, and other stresses, as well as hormonal signals. Interestingly, NAC genes weren't very active in male reproduction, especially in mature pollen, across different plants. We also discovered some NAC genes that reacted to heat stress in a similar way in very different plants, like the liverwort Marchantia polymorpha and rice (Oryza sativa). This journey tells us that the ways plants use NAC genes to handle stress and grow have been around since the early days of plants moving onto land. These mechanisms are still important in today's crops.