Abstract
BackgroundMADS-box transcription factors (TFs) are the key regulators of multiple developmental processes in plants; among them, a chrysanthemum MADS-box TF CmANR1 has been isolated and described as functioning in root development in response to high nitrate concentration signals. However, how CmANR1 affects root and shoot development remains unclear.ResultsWe report that CmANR1 plays a positive role in root system development in chrysanthemum throughout the developmental stages of in vitro tissue cultures. Metabolomics combined with transcriptomics assays show that CmANR1 promotes robust root system development by facilitating nitrate assimilation, and influencing the metabolic pathways of amino acid, glycolysis, and the tricarboxylic acid cycle (TCA) cycle. Also, we found that the expression levels of TFs associated with the nitrate signaling pathways, such as AGL8, AGL21, and LBD29, are significantly up-regulated in CmANR1-transgenic plants relative to the wild-type (WT) control; by contrast, the expression levels of RHD3-LIKE, LBD37, and GATA23 were significantly down-regulated. These results suggest that these nitrate signaling associated TFs are involved in CmANR1-modulated control of root development. In addition, CmANR1 also acts as a positive regulator to control shoot growth and development.ConclusionsThese findings provide potential mechanisms of MADS-box TF CmANR1 modulation of root and shoot development, which occurs by regulating a series of nitrate signaling associated TFs, and influencing the metabolic pathways of amino acid and glycolysis, as well as TCA cycle and nitrate assimilation.
Highlights
MADS-box transcription factors (TFs) are the key regulators of multiple developmental processes in plants; among them, a chrysanthemum MADS-box TF CmANR1 has been isolated and described as functioning in root development in response to high nitrate concentration signals
We have observed and measured the root growth and developmental parameters of several periods of both transgenic and WT chrysanthemum (10-day-old in vitro tissue cultures, 20day-old in vitro tissue cultures, and 40-day-old in vitro tissue cultures), and it seemed that CmANR1 could respond quickly to the higher concentration of nitrate (10 mM, under the culture condition) and its positive role in root development was obvious at the initial stage of growth, which might continue into the later growth and development in transgenic plants
As CmANR1-overexpression in the transgenic plants was triggered by a 35S promoter in our study, we could not determine whether the growth advantages of the transgenic plants on the shoot were due to the direct regulation of CmANR1 on other molecular players in shoots or due to the indirect stimulative effect of more nutrients and water uptake by the more extensive root system of transgenic plants
Summary
MADS-box transcription factors (TFs) are the key regulators of multiple developmental processes in plants; among them, a chrysanthemum MADS-box TF CmANR1 has been isolated and described as functioning in root development in response to high nitrate concentration signals. TFs are crucial for root plasticity and development by regulation of multiple target genes, and their mutation or gain of function might result in dramatic phenotypic modifications responding to the specific conditions [8,9,10]. MADS-box transcription factors are key regulators of multiple developmental processes in plants [11], but their contributions to root development are rarely uncovered. ANR1, a MADS-box transcription factor gene, has been reported to play roles in lateral root development under nitrate-rich situations in several plant species, but so far, its underlying regulatory mechanism of root development has been somewhat restricted to unclear auxin-related biological processes in the nitrate signaling pathway [12]. At present, to connect ANR1 to both root and shoot development has become a new challenge
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