Molecular Mechanism of the Underlying Regulatory Long-distance Shoot-root Communication Is Revealed

Although plant shoots and roots follow distinct developmental trajectories, their biology is tightly coordinated to optimize whole-plant performance in a fluctuating environment. The coordination of metabolic assimilation is of key importance: shoots fix atmospheric carbon (C; CO₂), roots acquire soil ionic nitrogen (N; predominantly nitrate, NO₃^-. The regulation of rates of N and C acquisition is known to be tightly coupled, with light regulating both processes. However, the molecular mechanisms of the underlying regulatory long-distance shoot-root communication remain unknown.

 

A team led by Dr. FU Xiangdong of the State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology (IGDB), Chinese Academy of Sciences, recently reported that a bZIP transcription factor ELONGATED HYPOCOTYL5 (HY5) is a shoot-root mobile signal that mediates light-regulated coupling of shoot growth and C assimilation with root growth and N uptake.

 

As a shoot-root phloem-mobile signal, HY5 mediates light regulation of root growth and NO₃^- uptake through activating root NRT2.1, a gene encoding a high-affinity nitrate transporter.  HY5 also affects sucrose metabolism and shoot-root transport by promoting the expression levels of TPS1, a gene encoding trehalose-6-phosphate synthase, and SWEET11 and SWEET12, genes encoding sucrose efflux transporters, by binding to the their promoters.

 

It is known that C status regulates N status. Further results indicate that HY5 responds to sugar signals in the regulation of NRT2.1-dependent NO₃^- uptake, thus contributing to the coordinated homeostatic balancing of C and N metabolism, and HY5 regulates the coordination of shoot and root growth and C and N acquisition throughout the plant life cycle. In particular, HY5 maintains homeostatic balance of C and N metabolism at varying light fluence.

 

HY5 is already known to integrate multiple phytohormonal and environmental signaling inputs in the control of plant growth and development. These discoveries that HY5 is a mobile signal adds further dimension to this knowledge and HY5 mobility mediates homeostatic coordination of C and N metabolism enhances understanding of how plant C and N nutrient balance is maintained in fluctuating environments. This study suggests novel strategies for the improvement of nutrient-use efficiency in crops.

 

The work entitled “Shoot-to-Root Mobile Transcription Factor HY5 Coordinates Plant Carbon and Nitrogen Acquisition” was published on Current Biology on March 7, 2016 (DOI:10.1016/j.cub.2015.12.066).

 

This research was supported by the grants from National Basic Research Program of China and the National Natural Science Foundation.

 

 

 

Mobile HY5 coordinates light-responsive carbon and

nitrogen metabolism, and hence shoot and root growth. (Image by IGDB)

 

 

Contact:

Dr. FU Xiangdong

E-mail: xdfu@genetics.ac.cn