Abstract
BackgroundThe embryonic temporal regulator FUSCA3 (FUS3) plays major roles in the establishment of embryonic leaf identity and the regulation of developmental timing. Loss-of-function mutations of this B3 domain transcription factor result in replacement of cotyledons with leaves and precocious germination, whereas constitutive misexpression causes the conversion of leaves into cotyledon-like organs and delays vegetative and reproductive phase transitions.ResultsHerein we show that activation of FUS3 after germination dampens the expression of genes involved in the biosynthesis and response to the plant hormone ethylene, whereas a loss-of-function fus3 mutant shows many phenotypes consistent with increased ethylene signaling. This FUS3-dependent regulation of ethylene signaling also impinges on timing functions outside embryogenesis. Loss of FUS3 function results in accelerated vegetative phase change, and this is again partially dependent on functional ethylene signaling. This alteration in vegetative phase transition is dependent on both embryonic and vegetative FUS3 function, suggesting that this important transcriptional regulator controls both embryonic and vegetative developmental timing.ConclusionThe results of this study indicate that the embryonic regulator FUS3 not only controls the embryonic-to-vegetative phase transition through hormonal (ABA/GA) regulation but also functions postembryonically to delay vegetative phase transitions by negatively modulating ethylene-regulated gene expression.
Highlights
The embryonic temporal regulator FUSCA3 (FUS3) plays major roles in the establishment of embryonic leaf identity and the regulation of developmental timing
Downstream effectors of FUS3 The discovery that FUS3 misexpression outside embryogenesis can influence vegetative leaf identity suggests that potential FUS3-dependent downstream effectors can be identified through whole-genome microarray analysis [11]
The introduction of the ein2 mutation did suppress defects in vegetative phase change compared to the fus3 single mutant as measured by leaf profiles, blade-to-petiole ratios and abaxial trichome appearance (Figures 5A to 5C). These results suggest that increased ethylene signaling does contribute to the advanced vegetative phase transition phenotype observed in fus3
Summary
The embryonic temporal regulator FUSCA3 (FUS3) plays major roles in the establishment of embryonic leaf identity and the regulation of developmental timing. Spatial patterning in most multicellular organisms requires genes to both establish regions of cell differentiation and specify cellular fate. Homeotic genes are required to establish boundaries during temporal patterning, whereas heterochronic. Higher plants are well-suited for identifying genes involved in developmental timing because they continually produce distinguishable organs throughout the life cycle, whose fates are dependent on the time of emergence [3]. The types of leaves that emerge over time often show distinctive developmental changes that allow them to be classified into juvenile and adult leaves. Genetic analysis in Arabidopsis thaliana has identified a myriad of genes that converge to control the juvenile to adult leaf transitions and the switch of the vegetative meristem to reproductive development [5]
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