Light and Dark Conditions Reveal Distinct Components of the Phosphate Starvation Re-sponse in Soybean Roots

Because sucrose transport from shoot to root contributes to long-distance Pi-deficiency signaling, we asked whether soybean roots can still respond to −P when sucrose supply is restricted. To limit sucrose transport to the root, hydroponically grown plants were exposed to +P or −P conditions for 30 h under light or darkness, with darkness suppressing photosynthetic sucrose production.

Root transcriptomes were profiled using Oxford Nanopore cDNA sequencing across four biological replicates. Principal component analysis showed that light conditions explained most transcriptomic variance, whereas Pi status contributed a smaller component. Under light, Pi defi-ciency activated canonical markers of the Pi starvation response, such as PHT1, PHO1, and PTEN2α.