Recently, Professor Shaojian Zheng’s team at the College of Life Sciences, Zhejiang University, in collaboration with Professor Shuichi Yanagisawa’s team at the University of Tokyo, published online in Nature Plants the research article titled “Trans-organ analysis of gene co-expression networks reveals a mobile long-distance regulator that balances shoot and root development in Arabidopsis”.
During the experiments, to prevent cellular shrinkage in acetone-fixed tissue sections, seedlings were transferred into a Jiupo plant growth chamber under precisely controlled environmental conditions.
They successfully developed the first systematic method to screen for long-distance mobile signaling factors in plants. Utilizing this platform, they constructed the first panoramic multi-organ nitrogen-responsive gene expression atlas. Within this framework, they precisely identified the transcription factor TGA7 as a crucial “messenger” that dynamically shuttles between shoots and roots to coordinate the plant’s integrated growth strategy under low nitrogen stress.
Core Breakthrough: From “Needle in a Haystack” to “Precise Navigation”
Traditional studies are often confined to single organs, limiting the understanding of inter-organ coordination. This study introduces an innovative trans-organ gene co-expression network analysis, integrating shoot and root transcriptomic data from 17 Arabidopsis ecotypes under both nitrogen-sufficient and nitrogen-deficient conditions. For the first time, the shoot-derived transcription factors governing root nitrogen responses were mapped. From over 2,000 shoot transcription factors, the researchers pinpointed five key regulators significantly affecting root responses to nitrogen deficiency, each validated individually. This method functions like a “genetic GPS” for researchers, dramatically enhancing the efficiency of identifying long-distance regulatory factors, bridging a technical gap in plant signal identification, and providing a universal template for screening other long-distance signaling molecules such as hormones or peptides.
Figure 1. Root low-nitrogen response network integrated from shoot TFs and core transcription factor screening.
Mechanistic Insights: TGA7’s Dual Role—Orchestrating Energy Production and Nitrogen Acquisition
Among the candidate transcription factors, the bZIP family member TGA7 stood out. Its expression in shoots strongly correlated with multiple key nitrogen-responsive genes in roots, including nitrate transporters. Through transgenic and grafting experiments, the study confirmed that the TGA7 protein moves within the plant body and coordinates shoot and root growth via dual mechanisms:
In the shoot, TGA7 directly activates photosynthesis-related genes such as Lhcb2.3 and Lhcb6, enhancing energy synthesis.
In the root, TGA7 directly activates NRT2.1, and indirectly boosts NRT2.4/NRT2.5 via regulation of the transcription factor NF-YA10, significantly enhancing nitrate uptake.
Notably, under nitrogen deficiency, TGA7 expression in the shoot’s vascular tissues is markedly upregulated. TGA7 protein is transported via the phloem to roots, where it suppresses excessive shoot growth while promoting root development and nitrogen uptake—thus achieving precise resource allocation under resource limitation.
Figure 2. Schematic model of the multiple growth-regulatory effects of the mobile signal TGA7.
Implications and Outlook
This study not only unveils a scalable, cross-organ screening platform that transcends traditional organ-specific research, but also elucidates how the molecular “messenger” TGA7 coordinates resource allocation between different organs. It provides novel genetic resources and theoretical guidance for improving crop stress resistance and nutrient use efficiency. In the future, this approach could be extended to screen for long-distance regulators of various agronomic traits. By finely tuning the expression and transport of such “messengers,” we can achieve optimized coordination between shoot and root systems, contributing to global food security and sustainable agricultural development.