Abstract
The At-Hook Motif Nuclear Localized Protein (AHL) gene family encodes embryophyte-specific nuclear proteins with DNA binding activity. They modulate gene expression and affect various developmental processes in plants. We identify AHL18 (At3G60870) as a developmental modulator of root system architecture and growth. AHL18 is involved in regulation of the length of the proliferation domain and number of dividing cells in the root apical meristem and thereby, cell production. Both primary root growth and lateral root development respond according to AHL18 transcription level. The ahl18 knock-out plants show reduced root systems due to a shorter primary root and a lower number of lateral roots. This change results from a higher number of arrested and non-developing lateral root primordia (LRP) rather than from a decreased LRP initiation. The over-expression of AHL18 results in a more extensive root system, longer primary roots, and increased density of lateral root initiation events. AHL18 is thus involved in the formation of lateral roots at both LRP initiation and their later development. We conclude that AHL18 participates in modulation of root system architecture through regulation of root apical meristem activity, lateral root initiation and emergence; these correspond well with expression pattern of AHL18.
Highlights
The root system is essential for plant anchorage, water and nutrition acquisition, and mediating interactions with the soil environment and microorganisms
The At-Hook Motif Nuclear Localized Protein (AHL) proteins contain a unique combination of one or two AT-hook domains, allowing them to bind to the minor groove of DNA in the specific AT rich sites and in Plants and prokaryotes conserved domain (PPC), which is responsible for their nuclear localization and interaction with other proteins
Identification of AHL18 as a Gene Involved in Root Development and Analysis of its Expression
Summary
The root system is essential for plant anchorage, water and nutrition acquisition, and mediating interactions with the soil environment and microorganisms. The AHL proteins contain a unique combination of one or two AT-hook domains, allowing them to bind to the minor groove of DNA in the specific AT rich sites and in Plants and prokaryotes conserved domain (PPC), which is responsible for their nuclear localization and interaction with other proteins They can either, form homo- or hetero-oligomers with other AHLs or interact with some transcription factors [13,15]. An intriguing property of AHL activity is the multilevel mode of their action (epigenetics, interaction with a transcription factor, simultaneous function as an activator and repressor of transcription) frequently bridging various regulatory pathways [15,16] This modus operandi makes them rather potent and complex regulators, with localization of expression, as well as interactions between different AHLs playing a crucial role. There is clear regulatory function of AHl18 in the root apical meristem activity, onset of differentiation, LRP initiation and their latter development
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