AUTHOR=Huai Zexun , Peng Lishun , Wang Sheliang , Zhao Hua , Shi Lei , Xu Fangsen 

TITLE=Identification and Characterization of an Arabidopsis thaliana Mutant lbt With High Tolerance to Boron Deficiency

JOURNAL=Frontiers in Plant Science

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2018.00736

DOI=10.3389/fpls.2018.00736

ISSN=1664-462X

ABSTRACT=<p>Boron (B) is an essential micronutrient of plants. In the present study, we characterized an <italic>Arabidopsis</italic> mutant <italic>lbt</italic> with significant <bold>l</bold>ow<bold>-b</bold>oron <bold>t</bold>olerance that was identified based on our previous mapping of QTL for B efficiency in <italic>Arabidopsis</italic>. Multiple nutrient-deficiency analyses point out that <italic>lbt</italic> mutant is insensitive to only B-limitation stress. Compared with wild-type Col-0, the fresh weight, leaf area, root length and root elongation rate of <italic>lbt</italic> mutant were significantly improved under B deficiency during vegetative growth. <italic>lbt</italic> mutant also showed the improvements in plant height, branches and inflorescences compared with Col-0 during the reproductive stage under B limitation. Ultrastructure analysis of the leaves showed that starch accumulation in <italic>lbt</italic> mutant was significantly diminished compared with Col-0. Furthermore, there were no significant differences in the expression of transporter-related genes and B concentrations between Col-0 and <italic>lbt</italic> mutant under both normal B and low-B conditions. These results suggest that <italic>lbt</italic> mutant has a lower B demand than Col-0. Genetic analysis suggests that the low-B tolerant phenotype of <italic>lbt</italic> mutant is under the control of a monogenic recessive gene. Based on the high-density SNP linkage genetic map, only one QTL for low-B tolerance was mapped on chromosome 4 between 10.4 and 14.8 Mb. No any reported B-relative genes exist in the QTL interval, suggesting that a gene with unknown function controls the tolerance of <italic>lbt</italic> to B limitation. Taken together, <italic>lbt</italic> is a low-B tolerant mutant that does not depend on the uptake or transport of B and is controlled by a monogenic recessive gene mapped on chromosome 4, and cloning and functional analysis of <italic>LBT</italic> gene are expected to reveal novel mechanisms for plant resistance to B deficiency.</p>