ABSTRACT
mRNA methylation at the N6-position of adenosine (m6A) enables multiple layers of post-transcriptional gene control, often via RNA-binding proteins that use a YT521-B homology (YTH) domain for specific m6A recognition. In Arabidopsis, normal leaf morphogenesis and rate of leaf formation require m6A and the YTH-domain proteins ECT2, ECT3 and ECT4. In this study, we show that ect2/ect3 and ect2/ect3/ect4 mutants also exhibit slow root and stem growth, slow flower formation, defective directionality of root growth, and aberrant flower and fruit morphology. In all cases, the m6A-binding site of ECT proteins is required for in vivo function. We also demonstrate that both m6A methyltransferase mutants and ect2/ect3/ect4 exhibit aberrant floral phyllotaxis. Consistent with the delayed organogenesis phenotypes, we observe particularly high expression of ECT2, ECT3 and ECT4 in rapidly dividing cells of organ primordia. Accordingly, ect2/ect3/ect4 mutants exhibit decreased rates of cell division in leaf and vascular primordia. Thus, the m6A-ECT2/ECT3/ECT4 axis is employed as a recurrent module to stimulate plant organogenesis, at least in part by enabling rapid cellular proliferation.
Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Organogenesis, Plant/genetics , Adenosine/metabolism , Arabidopsis/growth & development , Arabidopsis Proteins/antagonists & inhibitors , Arabidopsis Proteins/genetics , Binding Sites , Cell Proliferation , Flowers/growth & development , Flowers/metabolism , Gene Expression Regulation, Plant , Intracellular Signaling Peptides and Proteins/genetics , Methylation , Methyltransferases/genetics , Methyltransferases/metabolism , Mutagenesis, Site-Directed , Plant Leaves/cytology , Plant Leaves/growth & development , Plant Leaves/metabolism , Plant Roots/growth & development , Plant Roots/metabolism , Plant Stems/growth & development , Plant Stems/metabolism , Plants, Genetically Modified/growth & development , Plants, Genetically Modified/metabolism , Protein Binding , RNA Interference , RNA, Small Interfering/metabolism , RNA-Binding Proteins/antagonists & inhibitors , RNA-Binding Proteins/genetics , RNA-Binding Proteins/metabolismABSTRACT
MicroProteins are small proteins that contain a single protein domain and are related to larger, often multi-domain proteins. At the molecular level, microProteins act by interfering with the formation of higher order protein complexes. In the past years, several microProteins have been identified in plants and animals that strongly influence biological processes. Due to their ability to act as dominant regulators in a targeted manner, microProteins have a high potential for biotechnological use. In this review, we present different ways in which microProteins are generated and we elaborate on techniques used to identify and characterize them. Finally, we give an outlook on possible applications in biotechnology.
Subject(s)
Alternative Splicing , Biotechnology/methods , Computational Biology/methods , Proteins/genetics , Animals , Humans , Open Reading Frames/genetics , Proteins/metabolism , Proteolysis , RNA Isoforms/geneticsABSTRACT
Protein farnesylation is central to molecular cell biology. In plants, protein farnesyl transferase mutants are pleiotropic and exhibit defective meristem organization, hypersensitivity to the hormone abscisic acid, and increased drought resistance. The precise functions of protein farnesylation in plants remain incompletely understood because few relevant farnesylated targets have been identified. Here, we show that defective farnesylation of a single factor-heat-shock protein 40 (HSP40), encoded by the J2 and J3 genes-is sufficient to confer ABA hypersensitivity, drought resistance, late flowering, and enlarged meristems, indicating that altered function of chaperone client proteins underlies most farnesyl transferase mutant phenotypes. We also show that expression of an abiotic stress-related microRNA (miRNA) regulon controlled by the transcription factor SPL7 requires HSP40 farnesylation. Expression of a truncated SPL7 form mimicking its activated proteolysis fragment of the membrane-bound SPL7 precursor partially restores accumulation of SPL7-dependent miRNAs in farnesyl transferase mutants. These results implicate the pathway directing SPL7 activation from its membrane-bound precursor as an important target of farnesylated HSP40, consistent with our demonstration that HSP40 farnesylation facilitates its membrane association. The results also suggest that altered gene regulation via select miRNAs contributes to abiotic stress-related phenotypes of farnesyl transferase mutants.
Subject(s)
Abscisic Acid/physiology , Arabidopsis Proteins/metabolism , HSP40 Heat-Shock Proteins/metabolism , Meristem/metabolism , Arabidopsis/anatomy & histology , Arabidopsis/genetics , Arabidopsis/growth & development , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Cell Membrane/metabolism , DNA-Binding Proteins/metabolism , Droughts , Farnesyltranstransferase/genetics , HSP90 Heat-Shock Proteins/genetics , Meristem/anatomy & histology , MicroRNAs/metabolism , Mutation , Prenylation , Signal Transduction , Transcription Factors/metabolismABSTRACT
Leaves are present in all land plants and are specialized organs for light harvesting. They arise at the flanks of the shoot apical meristem (SAM), and develop into lamina structures that exhibit adaxial/abaxial (upper/lower side of the leaf) polarity. At the molecular level, an intricate regulatory network determines ad-/abaxial polarity in Arabidopsis thaliana leaves, where the Class III Homeodomain Leucine Zipper (HD-ZIPIII) and KANADI (KAN) proteins are key mediators. The HD-ZIPIII REVOLUTA (REV) is expressed in the adaxial domain of lateral organs, whereas KAN1 is involved in abaxial differentiation. The REV/KAN1 module directly and antagonistically regulates the expression of several genes involved in shade-induced growth and auxin biosynthetic enzymes.
