Among five tomato cultivars, the responses to low iron (Fe) of the main Fe-uptake proteins and total protein in roots correlate with effects on biomass and chlorophyll

Authors: HECKATHORN, SCOTT - University Of Toledo; KOSTIC, EMINA - University Of Toledo; Boldt, Jennifer

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2026
Publication Date: 9/5/2026
Citation: Heckathorn, S., Kostic, E., Boldt, J.K. 2026. Among five tomato cultivars, the responses to low iron (Fe) of the main Fe-uptake proteins and total protein in roots correlate with effects on biomass and chlorophyll. Horticulturae. 12. Article 1123. https://doi.org/10.3390/horticulturae12091123.
DOI: https://doi.org/10.3390/horticulturae12091123

Interpretive Summary: Tomato is an economically-important horticultural crop in the United States and worldwide. Tomato is susceptible to iron deficiency, which reduces yield and fruit quality. Rapid and inexpensive molecular biomarkers that can be used to improve crop tolerance to iron stress are still rare. We examined the responses of five tomato cultivars to low iron. The response of certain iron-uptake proteins in their roots scaled with plant tolerance to low iron. Hence, these proteins may be useful biomarkers that plant breeders can use to identify new tomato cultivars that have improved tolerance to low iron.

Technical Abstract: Nutrient-uptake proteins (NUPs) have the potential to serve as biomarkers for crop improvement, with most studies to date focusing on NUP gene sequence or mRNA levels. In this study, we examined if protein levels of the main iron (Fe)-uptake proteins in roots scaled with sensitivity to Fe deficiency among five tomato (Solanum lycopersicum) cultivars (‘Abraham Lincoln’, ‘Big Boy’, ‘Cherokee Purple’, ‘Marzano’, and ‘Roma’). Plants were grown hydroponically with low or medium Fe (0.5 or 50 'M) for two weeks. On average across cultivars, biomass, shoot Fe concentration ([Fe]), and leaf chlorophyll concentration (leaf [chl]) were lower at low vs. medium Fe, while root-to-shoot ratio (R/S) responses were variable, and the concentrations of the main Fe-uptake proteins in roots [Iron Regulated Transporter (IRT), plasma-membrane H+-ATPase (H+-ATPase), and Ferric Reduction Oxidase (FRO)] were lower at low vs. medium Fe. Among cultivars, the percent decrease in plant fresh mass at low (compared to medium) Fe was inversely correlated with the percent increase in levels of IRT (r = -0.93, P = 0.02) and, to a lesser extent, FRO (r = -0.82, P = 0.09), but was not correlated with percent change in levels of H+-ATPase (P = 0.34). In comparison, the percent change in leaf [chl], a common biomarker for Fe deficiency, and fresh biomass were positively correlated (r =0.78, P=0.12). Thus, counterintuitively, tolerance to low Fe, on a biomass basis, was associated with a small or negligible increase in IRT and FRO levels among cultivars, indicating that: (1) other adaptations to low Fe rendered upregulation of IRT and FRO less necessary in tolerant cultivars, and (2) root IRT and, to a lesser extent, root FRO protein responses may serve as biomarkers for tolerance to low Fe.