Jumping DNA bits help some citrus trees grab scarce iron
Zhou X, Liu S, Fan Z, Peng J, Liu C
Crispr
If you've ever watched a citrus tree in alkaline or limey soil go yellow between the leaf veins, this research points to the genetic switch behind that iron-starved look, and why some rootstocks shrug it off while others struggle.
Some citrus trees are much better than others at pulling iron out of alkaline soil, which matters because iron-starved citrus develops pale, yellowing leaves and weak growth. Researchers discovered that tiny repetitive DNA snippets, leftover 'jumping genes,' landed right in front of the plant's iron-absorbing gene in a tough citrus variety and created new docking sites for stress-response proteins. When they disabled those docking proteins with gene editing, the plant lost its ability to ramp up iron uptake, showing these DNA snippets are the switch that makes the difference between an iron-sensitive and iron-tolerant tree.
Key Findings
Citrus wilsonii Tanaka shows rapid induction of the iron transporter gene CwIRT1 under low-iron conditions, unlike iron-sensitive Poncirus trifoliata
Two MITE transposable elements (MITE1 and MITE2) in the CwIRT1 promoter create binding sites for transcription factors CwERF12 and CwARF12, both upregulated under iron deficiency
CRISPR/Cas9 double knockout of CwERF12 and CwARF12 (but not single knockouts) suppresses CwIRT1 expression and reduces root iron uptake
chevron_right Technical Summary
Scientists found that 'jumping gene' fragments inserted near an iron-transporter gene in a hardy citrus species act as switches that turn on iron uptake when soil iron is scarce, helping explain why some citrus trees cope with alkaline soils better than others.
Abstract Preview
Original paper
MITE insertions generate enhancers for iron transporter CwIRT1 activation in citrus.
Iron (Fe) deficiency constrains citrus productivity in alkaline soils. Although the high-affinity Fe transporter IRT1 is essential for Fe acquisition, its transcriptional regulation in citrus remai...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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Citrus is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, such as citrons, mandarins, and pomelos. Many important citrus crops have been developed through extensive hybridization, including oranges, lemons, grapefruits, and limes, all of wh...