RAP2.3 Is Required for MYB51 and SIGMA3 Expression During the Response of Arabidopsis thaliana to Multifactorial Stress Combination

In nature, plants are subjected to multiple environmental stress factors simultaneously or sequentially. Recent studies revealed that when three or more stress factors impact a plant simultaneously (termed 'multifactorial stress combination'; MFSC), plant survival declines, even if the intensity of each individual stress involved in the MFSC is low. We previously identified RAP2.3 as a key transcription factor (TF) required for Arabidopsis thaliana survival, specifically under a MFSC of salt+excess light+heat stress (i.e., S + EL + HS). Here we report that RAP2.3 regulates the expression of SIGMA3, a nuclear-encoded factor that directs plastid RNA polymerase to specific plastid promoters, as well as MYB51, a key stress response TF involved in glucosinolate metabolism and oxidative stress responses, specifically during a MFSC of S + EL + HS. Like rap2.3 mutants, myb51 and sig3 mutants display significantly low survival rate specifically under the MFSC of S + EL + HS. Based on MYB51 gene regulatory network analysis and characterisation of jasmonic acid (JA) mutants, we further reveal that suppression of JA signalling could play an important role in promoting plant survival under conditions of S + EL + HS. Our findings uncover an additional layer of the response of plants to MFSC, as well as identify potential targets for breeding crops with enhanced tolerance to climate change.