Zinc (Zn) is an essential micronutrient for all organisms and serves as a cofactor for more than 300 enzymes. Cyclic guanosine 3′,5′-monophosphate (cGMP) is an important secondary messenger in animals and plants and has the multiple functions in regulating growth and development.

Previous study has indicated that both auxin and cGMP play a role in controlling root growth in plants. However, whether and how their interaction is involved in Zn-regulated root development remains unclear. 

In a new study published in Environmental and Experimental Botany, Prof. XU Jin and his team of Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences reported that excess Zn leads to auxin accumulation in root tips. 

“We investigated the roles of auxin and cGMP in excess Zn-regulated root system development”, said XU Jin, correspondence author of the study. 

The researchers found that excess Zn increases the expression of auxin biosynthesis-related genes and results in auxin accumulation in root tips.

Excess Zn also induced cGMP production, and elevated cGMP improved PIN4 abundance, thereby alleviating Zn-induced primary root growth inhibition and further promoting lateral root formation. 

The coordination of NO/ROS-mediated PCD and cGMP-mediated auxin redistribution modulates RSA and activity, thereby increasing Zn tolerance. The researchers thus proposed that modifying RSA is an effective route to improve crop tolerance and quality. 

The study provides insights into novel strategies for improving Zn tolerance and such an understanding is helpful for breeding and cultivation of Zn accumulators.