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The Levels of Boron‐Uptake Proteins in Roots are Correlated with Tolerance to Boron Stress in Barley
Author(s) -
Mishra Sasmita,
Heckathorn Scott,
Krause Charles
Publication year - 2015
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci2014.10.0706
Subject(s) - hordeum vulgare , biology , shoot , xylem , apoplast , symplast , botany , cultivar , horticulture , biochemistry , poaceae , cell wall
Boron (B) is an essential micronutrient required for plant growth and development. Recently, two major B‐uptake proteins, BOR1 and NIP5;1, have been identified and partially characterized. BOR1 is a high‐affinity B transporter involved in xylem loading in roots, and NIP5;1 is a major boric‐acid channel in the plasma membrane. The aim of the present study was to determine if plant tolerance to B stress (deficiency or toxicity) is correlated with natural levels of B‐uptake proteins in roots. We grew two barley ( Hordeum vulgare L.) cultivars that differ in tolerance to low and high B (Schooner and Clipper, respectively) at three B levels (sub‐, near‐, and supraoptimal), and then we determined the concentration of BOR1 and NIP5;1 in roots using enzyme‐linked immunosorbent assay (ELISA) and protein‐specific antibodies that we developed. Shoot and root biomass in Schooner decreased at high B, while shoot mass in Clipper decreased in low B. Differences between cultivars in tolerance to B stress were unrelated to the concentration of B in plant tissue or to effects of B on root total protein concentration. BOR1 content per unit total protein and per gram of root was greater in Clipper than Schooner, while NIP5;1 content was greater in Schooner. The estimated activity of BOR1 (B uptake per BOR1) did not differ between cultivars. These results show that whole‐plant tolerance to B deficiency and toxicity is correlated with levels of the major B‐uptake proteins in roots (BOR1 and NIP5;1). Hence, BOR1 and NIP5;1 can potentially be used as biomarkers to identify plant genotypes with enhanced tolerance to B stress (e.g., for agriculture or phytoremediation).