Iron deficiency changes regulatory mechanisms governing sieve element cell differentiation.

Plant cell differentiation incorporates environmental cues over time to optimize overall growth. Iron deficiency influences development, such as root hair, cortical, and endodermal cell differentiation. However, the mechanisms by which iron deficiency regulates cell differentiation are not well characterized. Root sieve elements serve as an excellent model for cell differentiation since all cells, from undifferentiated to differentiated, are present in a distinct cell file. Here, we use semi-automated image analysis to show that iron deficiency delays sieve element differentiation, particularly enucleation and cell wall thickening, and consequently delays phloem sap unloading to roots. Using Dynamic Bayesian modeling we also characterize how iron deficiency changes the fundamental structure of the gene regulatory network associated with sieve element differentiation. We identify DOF1.5 as a positive regulator of sieve element enucleation and, consequently, of root sap translocation. These results clarify how abiotic stress can influence overall plant growth as a consequence of negatively influencing vascular differentiation.