LAUSR

Plant root systems are essential for many physiological processes, including water and nutrient absorption. MADS-box transcription factor (TF) genes have been characterized as the important regulators of root development in plants; however, the underlying mechanism is largely unknown, including chrysanthemum. Here, it was found that the overexpression of CmANR1, a chrysanthemum MADS-box TF gene, promoted both adventitious root (AR) and lateral root (LR) development in chrysanthemum. Whole transcriptome sequencing analysis revealed a series of differentially expressed unigenes (DEGs) in the roots of CmANR1-transgenic chrysanthemum plants compared to wild-type plants. Functional annotation of these DEGs by alignment with Gene Ontology (GO) terms and biochemical pathway Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that CmANR1 TF exhibited “DNA binding” and “catalytic” activity, as well as participated in “phytohormone signal transduction”. Both chromatin immunoprecipitation–polymerase chain reaction (ChIP-PCR) and gel electrophoresis mobility shift assays (EMSA) indicated the direct binding of CmPIN2 to the recognition site CArG-box motif by CmANR1. Finally, a firefly luciferase imaging assay demonstrated the transcriptional activation of CmPIN2 by CmANR1 in vivo. Overall, our results provide novel insights into the mechanisms of MADS-box TF CmANR1 modulation of both AR and LR development, which occurs by directly regulating auxin transport gene CmPIN2 in chrysanthemum.Crop genetics: The genes that make chrysanthemum rootsResearchers in China have elucidated the genetic components controlling root development and architecture in chrysanthemum. A team at Shandong Agricultural University led by Da-gang Hu showed that the ANR1 gene promotes root branching as well as the development of additional roots from stem tissue. To identify other genes in the pathway, the team sequenced the RNA of plants with increased ANR1 expression to identify. They found 7,600 genes regulated by ANR1, including genes related to the plant hormone auxin, which is known to regulate root development. Further experiments revealed that ANR1 directly activates the PIN2 gene, which plays a role in determining the auxin distribution in the root. These findings not only advance our understanding of root development but will be valuable in efforts to breed varieties with improved root systems.HighlightMADS-box TF CmANR1 modulates both AR and LR development by directly regulating auxin transport gene CmPIN2 in chrysanthemum.