Transcriptomic Analysis Reveals the Key Role of Photosynthetic System Stability and Carotenoid Accumulation in Drought Tolerance in Maize.

Due to climate change, drought has emerged as a major threat to maize production globally. To explore the molecular mechanisms of drought stress adaptation at the maize seedling stage, previously identified as drought-tolerant inbred line CML323 and drought-sensitive inbred line CB2-49-1 were treated for 5 days (d) of drought treatment, and day 0 was defined as the time point when soil water content reached 60% of the field water content. After drought treatment, a change in carotenoid content was detected; at the same time, the leaves were collected for transcriptome analysis. Analyzing the mechanisms of drought stress response in the third leaf stage at physiological and transcriptional levels. The results showed that: (1) The number of DEGs in CML323 was 32.98% more than that in CB2-49-1 at 1 day of drought, which could rapidly activate the ABA signaling pathway to reduce water loss through stomatal closure and osmoregulation; (2) CML323 maintained the stable expression of photosystem genes and had a significantly higher carotenoid content of 21.43% compared to CB2-49-1 at 5 days of drought stress. And carotenoids synergized with substances such as isoprene to scavenge ROS; (3) Co-expression network analysis identified a hub gene, ZmPBS1, which may positively regulate drought stress. In summary, changes in the expression of crucial genes and signal transmission processes are induced by drought stress, thus initiating adaptive and protective mechanisms. These findings provide new insights into the mechanisms of carotenoid accumulation and photosynthetic stability under drought stress in maize.