Mechanisms regulating the boron nutritional status in rapeseed and Arabidopsis and their implications for the development of boron-efficient genotypes

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Boron (B) is an essential microelement for plants. Despite the use of modern fertilization methods, B-deficiency still causes losses in agricultural plant production. Even though many positive effects of B on plant growth and physiology have been reported, a large majority of B functions and the regulatory mechanisms controlling the B nutritional status remain unknown.The main objective of this project is to elucidate how the greatly B-deficiency-sensitive Brassica crop plants process and regulate their B status during vegetative and reproductive growth. In this context, the project aims at identifying the mode of action of B in mechanisms regulating the B status itself and at uncovering those mechanisms and underlying genes contributing to B-efficiency in different genotypes.Plant species subjected to investigation are the agronomically important crop plant Brassica napus (rapeseed) and its close relative the model plant Arabidopsis thaliana.Questions addressed within the scope of this project should lead to a detailed understanding of mechanisms controlling B uptake and allocation from the level of the whole plant down to the cellular level. Nodulin26-like Intrinsic Proteins (NIPs), which belong to the aquaporin protein family, are essential for B uptake and distribution. The systematic focus on the molecular and physiological characterization of B. napus NIPs will clarify their role in B transport and will identify novel NIP-associated mechanisms playing key roles in the B response network. To further resolve the mostly unknown impact of the B nutritional status on gene regulation and metabolism, RNA-sequencing will be performed on B-sufficient and B-deficient rapeseed plants. This will identify yet unknown B-responsive genes playing key roles in signalling pathways, B-dependent differentiation processes and mechanisms regulating the B homeostasis. QTL mapping (on a generated DH rapeseed population deriving from a cross between genotypes with contrasting B-efficiencies) and GWAS analyses (on data of an Arabidopsis accession panel) will be performed and the information will be used to identify loci and genes which are responsible for B-deficiency tolerance in rapeseed and Arabidopsis, respectively.Boric acid and arsenous acid (As) share the same NIP-mediated transport pathways. To assess whether it is possible to design B-specific NIP channels in order to generate crops with low concentrations of the toxic As mineral, we will investigate NIP channel characteristics which have an influence on metalloid transport selectivity in detail.This project has been designed to generate original knowledge on regulative mechanisms controlling the B homeostasis and on underlying genes. This project promises to contribute to the improvement of B management in the field, the optimization of agronomically relevant plant traits and the development of B-deficiency-tolerant genotypes.