Natural variation in salt-induced changes in root:shoot ratio reveals SR3G as a negative regulator of root suberization and salt resilience in <i>Arabidopsis</i>.

Abstract

Soil salinity is one of the major threats to agricultural productivity worldwide. Salt stress exposure alters root and shoots growth rates, thereby affecting overall plant performance. While past studies have extensively documented the effect of salt stress on root elongation and shoot development separately, here we take an innovative approach by examining the coordination of root and shoot growth under salt stress conditions. Utilizing a newly developed tool for quantifying the root:shoot ratio in agar-grown <i>Arabidopsis</i> seedlings, we found that salt stress results in a loss of coordination between root and shoot growth rates. We identify a specific gene cluster encoding domain-of-unknown-function 247 (DUF247), and characterize one of these genes as <u>S</u>alt <u>R</u>oot:shoot <u>R</u>atio <u>R</u>egulator <u>G</u>ene (SR3G). Further analysis elucidates the role of SR3G as a negative regulator of salt stress tolerance, revealing its function in regulating shoot growth, root suberization, and sodium accumulation. We further characterize that <i>SR3G</i> expression is modulated by <i>WRKY75</i> transcription factor, known as a positive regulator of salt stress tolerance. Finally, we show that the salt stress sensitivity of <i>wrky75</i> mutant is completely diminished when it is combined with <i>sr3g</i> mutation. Together, our results demonstrate that utilizing root:shoot ratio as an architectural feature leads to the discovery of a new stress resilience gene. The study's innovative approach and findings not only contribute to our understanding of plant stress tolerance mechanisms but also open new avenues for genetic and agronomic strategies to enhance crop environmental resilience.