The Tie-dyed pathway promotes symplastic trafficking in the phloem

Abstract

The tie-dyed1 (tdy1) and tdy2 mutants of maize exhibit leaf regions with starch hyperaccumulation and display unusual genetic interactions, suggesting they function in the same physiological process. Tdy2 encodes a putative callose synthase and is expressed in developing vascular tissues of immature leaves. Radiolabelling experiments and transmission electron microscopy (TEM) revealed symplastic trafficking within the phloem was perturbed at the companion cell/sieve element interface. Here, we show that as reported for tdy2 mutants, tdy1 yellow leaf regions display an excessive oil-droplet phenotype in the companion cells. Based on the proposed function of Tdy2 as a callose synthase, our previous work characterizing Tdy1 as a novel, transmembrane-localized protein, and the present findings, we speculate how TDY1 and TDY2 might interact to promote symplastic transport of both solutes and developmentally instructive macromolecules during vascular development at the companion cell/sieve element interface.

Keywords: :

• callose synthase
• companion cell
• maize
• oil droplet
• phloem
• plasmodesmata
• sieve element
• symplastic trafficking
• tie-dyed
• xylem

Disclosure of Potential Conflicts of Interest

No Potential conflicts of interest were disclosed

Financial Disclosure

This work was supported by the National Science Foundation Plant Genome Research Program (grant no. IOS-1025976 to D.M.B.).