Abstract
As sessile organisms, plants must adjust their growth to withstand several environmental conditions. The root is a crucial organ for plant survival as it is responsible for water and nutrient acquisition from the soil and has high phenotypic plasticity in response to a lack or excess of them. How plants sense and transduce their external conditions to achieve development, is still a matter of investigation and hormones play fundamental roles. Hormones are small molecules essential for plant growth and their function is modulated in response to stress environmental conditions and internal cues to adjust plant development. This review was motivated by the need to explore how Arabidopsis thaliana primary root differentially sense and transduce external conditions to modify its development and how hormone-mediated pathways contribute to achieve it. To accomplish this, we discuss available data of primary root growth phenotype under several hormone loss or gain of function mutants or exogenous application of compounds that affect hormone concentration in several abiotic stress conditions. This review shows how different hormones could promote or inhibit primary root development in A. thaliana depending on their growth in several environmental conditions. Interestingly, the only hormone that always acts as a promoter of primary root development is gibberellins.
Highlights
The roots, besides affording structural support to the plant, play crucial roles in the acquisition of nutrients and water as well as in the interaction with different organisms, reacting plastically to diverse stimuli [1]
As many previous reviews have described biosynthesis, catabolism, signaling, and transport of these hormones [13,14,15,16,17,18,19,20,21,22,23,24,25], we briefly describe the generalities of hormone function in root development and summarize the function and names of the proteins encoded by genes, whose loss and gain-of-function (LoF and GoF) mutants were analysed in this review (Tables S1 and S2)
This review showed the importance of the phytohormones and the crosstalk among them under different stress conditions to determine Arabidopsis primary root growth and plasticity
Summary
The roots, besides affording structural support to the plant, play crucial roles in the acquisition of nutrients and water as well as in the interaction with different organisms, reacting plastically to diverse stimuli [1]. While hormone gene regulation is fundamental to root development, we focused on phenotypic evidence regarding PR growth under either exogenous application of compounds that change the hormone concentration and examples of loss or gain of function mutants on key components of hormone pathways To this end, we first briefly delineate the hormone function in PR growth under control conditions and describe the different functional role of each phytohormones alone or in crosstalk with other hormones during Arabidopsis PR growth under different abiotic stress conditions, such as low water availability (osmotic, salt and cold), oxidative stress, metal stress, high temperature stress, soil alkalinity and nutrient condition. We have found with this approximation that GA is the only hormone that promotes primary root growth in all stress conditions described in this review
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