Environmental regulation of male fertility is mediated through Arabidopsis transcription factors bHLH89, 91, and 10.

Formation of functional pollen and successful fertilization rely on the spatial and temporal regulation of anther and pollen development. This process responds to environmental cues to maintain optimal fertility despite climatic changes. Arabidopsis transcription factors basic helix-loop-helix (bHLH) 10, 89, and 91 were previously thought to be functionally redundant in their control of male reproductive development, however here we show that they play distinct roles in the integration of light signals to maintain pollen development under different environmental conditions. Combinations of the double and triple bHLH10,89,91 mutants were analysed under normal (200 μmol m-2 s-1) and low (50 μmol m-2 s-1) light conditions to determine the impact on fertility. Transcriptomic analysis of a new conditionally sterile bhlh89,91 double mutant shows differential regulation of genes related to sexual reproduction, hormone signal transduction, and lipid storage and metabolism under low light. Here we have shown that bHLH89 and bHLH91 play a role in regulating fertility in response to light, suggesting that they function in mitigating environmental variation to ensure fertility is maintained under environmental stress.