Grafting reveals organ-autonomous and feedback roles of root phloem development in source-sink dynamics.
Bartusch K, Schreier TB, Fischer-Stettler M, Zeeman SC, Truernit E
Crop Improvement
PubMedBreeding crops with better-connected root plumbing could unlock higher yields by letting roots and leaves communicate more efficiently, meaning the tomatoes, wheat, and corn on your plate could grow more robustly with the same sunlight.
Plants move sugars made in leaves down to roots through tube-like channels. Researchers found that when those tubes in the roots are damaged, roots don't just starve — they also send faulty signals back to the leaves, causing the whole plant to grow poorly. This means root health and leaf productivity are locked in a conversation, not a one-way delivery system.
Key Findings
Root growth defects in phloem-deficient mutants are root-autonomous — grafting normal leaves onto mutant roots did not rescue root growth, proving the problem originates in the roots themselves.
Damaged root phloem restricted growth of healthy wild-type shoots grafted onto mutant roots, demonstrating that impaired sink tissue sends negative feedback signals that suppress source-leaf activity.
Carbon partitioning and phloem transport velocity were both reduced in mutants, with double-mutant (ops opl2) plants showing stronger defects than single-mutant (ops) plants, and only double-mutant root growth was partially rescued by external sucrose.
chevron_right Technical Summary
Scientists discovered that roots need well-functioning internal plumbing (phloem) not just to receive sugar from leaves, but to send signals back that tell leaves how much sugar to produce — a two-way communication system that controls whole-plant growth.
Abstract Preview
Carbon fixed in source leaves is partitioned between local use and long-distance transport through the phloem to heterotrophic sinks such as roots. Here, we investigated how mild defects in sink ph...
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