Abstract
MONOPTEROS (MP) is an auxin-responsive transcription factor that is required for primary root formation and vascular development, whereas Dof5.8 is a Dof-class transcription factor whose gene is expressed in embryos as well as the pre- and procambial cells in the leaf primordium in Arabidopsis thaliana. In this study, it is shown that MP directly activates the Dof5.8 promoter. Although no apparent phenotype of the single dof5.8 mutants was found, phenotypic analysis with the mp dof5.8 double mutants revealed that mutations within Dof5.8 enhanced the phenotype of a weak allele of mp, with an increase in the penetrance of the 'rootless' phenotype and a reduction in the number of cotyledons. Furthermore, interestingly, although mp mutants showed reduced vascular pattern complexity in cotyledons, the mp dof5.8 double mutants displayed both more simplex and more complex vascular patterns in individual cotyledons. These results imply that the product of Dof5.8 whose expression is regulated by MP at least in part might be involved in multiple processes controlled by MP.
Highlights
MONOPTEROS (MP), which is known as auxin response factor 5 (ARF5) of the ARF family, is a key regulator that functions in the establishment of vasculature and body patterns in embryonic and post-embryonic development in Arabidopsis thaliana (Hardtke and Berleth, 1998; Ulmasov et al, 1999a, b)
MONOPTEROS (MP) is an auxin-responsive transcription factor that is required for primary root formation and vascular development, whereas Dof5.8 is a Dof-class transcription factor whose gene is expressed in embryos as well as the pre- and procambial cells in the leaf primordium in Arabidopsis thaliana
Because the synthetic auxin response element, DR5, induces a similar expression pattern in leaves (Ulmasov et al, 1997b; Mattsson et al, 2003; Scarpella et al, 2006), the expression patterns produced by a GUS reporter gene under the control of either the Dof5.8 promoter or DR5 during the development of the first leaf primordia were compared (Fig. 1A)
Summary
MONOPTEROS (MP), which is known as auxin response factor 5 (ARF5) of the ARF family, is a key regulator that functions in the establishment of vasculature and body patterns in embryonic and post-embryonic development in Arabidopsis thaliana (Hardtke and Berleth, 1998; Ulmasov et al, 1999a, b). Consistent with the diverse functions of MP in embryonic root initiation, lateral organ initiation, shoot meristem cell regulation, and vascular patterning in leaves (Berleth and Jürgens, 1993; Przemeck et al, 1996; Hardtke et al, 2004; Schuetz et al, 2008), recent intensive studies revealed that MP activates the expression of DRN involved in cell patterning in embryos (Cole et al, 2009), TMO genes crucial for embryonic root initiation (Schlereth et al, 2010), and LFY for flower initiation (Yamaguchi et al, 2013), and represses the expression of ARR7 and ARR15, negative regulators of cytokinin. Target genes of MP probably vary depending on organ, tissue type, or developmental stage, and MP functions and MP-induced regulation still remain largely unknown
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