Isochorismate synthase (ICS) converts chorismate to isochorismate for the biosynthesis of phylloquinone, an essential cofactor for photosynthetic electron transport. ICS is also required for salicylic acid (SA) synthesis during Arabidopsis defense. In several other species, including Populus, SA is derived primarily from the phenylpropanoid pathway. We therefore sought to investigate ICS regulation in Populus to learn the extent of ICS involvement in SA synthesis and defense. Arabidopsis harbors duplicated AtICS genes that differ in their exon-intron structure, basal expression, and stress inducibility. In contrast, we found a single ICS gene in Populus and six other sequenced plant genomes, pointing to the AtICS duplication as a lineage-specific event. The Populus ICS encodes a functional plastidic enzyme, and was not responsive to stresses that stimulated phenylpropanoid accumulation. Populus ICS underwent extensive alternative splicing that was rare for the duplicated AtICSs. Sequencing of 184 RT-PCR Populus clones revealed 37 alternative splice variants, with normal transcripts representing approximately 50% of the population. When expressed in Arabidopsis, Populus ICS again underwent alternative splicing, but did not produce normal transcripts to complement AtICS1 function. The splice-site sequences of Populus ICS are unusual, suggesting a causal link between junction sequence, alternative splicing, and ICS function. We propose that gene duplication and alternative splicing of ICS evolved independently in Arabidopsis and Populus in accordance with their distinct defense strategies. AtICS1 represents a divergent isoform for inducible SA synthesis during defense. Populus ICS primarily functions in phylloquinone biosynthesis, a process that can be sustained at low ICS transcript levels.
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http://dx.doi.org/10.1073/pnas.0906869106 | DOI Listing |
ACS Chem Neurosci
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Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208, United States.
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Department of Breast Surgery, Second Affiliated Hospital and Cancer Institute (Provincial Key Laboratory of Tumor Microenvironment and Immunotherapy, Key Laboratory of Cancer Prevention & Intervention, National Ministry of Education), Zhejiang University School of Medicine, Hangzhou, China.
Background: Quaking (QKI) is a member of the signal transduction and activators of RNA (STAR) family, performing a crucial multifunctional regulatory role in alternative splicing, mRNA precursor processing, mRNA transport and localization, mRNA stabilization, and translation during tumour progression. Abnormal QKI expression or fusion mutations lead to aberrant RNA and protein expression, thereby promoting tumour progression. However, in many types of tumour, QKI played a role as tumour suppressor, the regulatory role of QKI in tumour progression remains ambiguous.
View Article and Find Full Text PDFCell Rep
December 2024
Department of Non-coding RNAs, Institute of Bioorganic Chemistry of the Polish Academy of Sciences, 61-704 Poznan, Poland. Electronic address:
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View Article and Find Full Text PDFCurr Opin Insect Sci
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Department of Entomology, College of Plant Protection, China Agricultural University, Beijing, China. Electronic address:
Social insects often show remarkable behavioral plasticity, which is closely associated with their respective castes. The underpinnings of this plasticity are complex, involving genetic differences among individuals within a colony and regulation of gene expression at multiple levels. Post-transcriptional regulation, which increases the complexity of the transcriptome, plays a crucial role in the multilayer regulatory network that influences social insect behavior.
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