As a gaseous diatomic radical, nitric oxide (NO) is an essential endogenous signalling molecule involved in multiple physiological processes in plants, including growth, development, and response to environmental stresses. However, the molecular mechanism underlying NO-mediated stress resistance remains largely unclear.   

To gain insight into NO-mediated stress tolerance, Dr. SHI Haitao, under the supervision of Prof. CHAN Zhulong at Wuhan Botanical Garden used NO synthase (nNOS) transgenic Arabidopsis plants with increased in vivo NO content for physiological and transcriptomic analyses in the current study. 

Firstly, the nNOS transgenic Arabidopsis plants displayed high levels of osmolytes and increased antioxidant enzyme activities.  

Secondly, transcriptomic analysis identified 601 or 510 genes that were differentially expressed as a consequence of drought stress or nNOS transformation, respectively. Pathway and gene ontology (GO) term enrichment analyses revealed that genes involved in photosynthesis, redox, stress, and phytohormone and secondary metabolism were greatly affected by the nNOS transgene. Several CBF genes and members of zinc finger gene families, which are known to regulate transcription in the stress response, were changed by the nNOS transgene.  

Interestingly, genes regulated by both the nNOS transgene and abscisic acid (ABA) treatments were compared and identified, including those for two ABA receptors (AtPYL4 and AtPYL5). Moreover, overexpression of AtPYL4 and AtPYL5 enhanced drought resistance, antioxidant enzyme activity, and osmolyte levels. These finding increased our understanding of the physiological and molecular mechanisms by which NO mediates the drought stress response in Arabidopsis. 

 Results entitled “Constitutive production of nitric oxide leads to enhanced drought stress resistance and extensive transcriptional reprogramming in Arabidopsis” were published in Journal of Experimental Botany.