RESUMEN
The regulatory particle (RP) of the 26S proteasome contains a heterohexameric ring of AAA-ATPases (RPT1-6) that unfolds and inserts substrates into the core protease (CP) for degradation. Through genetic analysis of the Arabidopsis thaliana gene pair encoding RPT2, we show that this subunit plays a critical role in 26S proteasome assembly, histone dynamics, and plant development. rpt2a rpt2b double null mutants are blocked in both male and female gamete transmission, demonstrating that the subunit is essential. Whereas rpt2b mutants are phenotypically normal, rpt2a mutants display a range of defects, including impaired leaf, root, trichome, and pollen development, delayed flowering, stem fasciation, hypersensitivity to mitomycin C and amino acid analogs, hyposensitivity to the proteasome inhibitor MG132, and decreased 26S complex stability. The rpt2a phenotype can be rescued by both RPT2a and RPT2b, indicative of functional redundancy, but not by RPT2a mutants altered in ATP binding/hydrolysis or missing the C-terminal hydrophobic sequence that docks the RPT ring onto the CP. Many rpt2a phenotypes are shared with mutants lacking the chromatin assembly factor complex CAF1. Like caf1 mutants, plants missing RPT2a or reduced in other RP subunits contain less histones, thus implicating RPT2 specifically, and the 26S proteasome generally, in plant nucleosome assembly.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/genética , Células Germinativas de las Plantas/crecimiento & desarrollo , Complejo de la Endopetidasa Proteasomal/metabolismo , Adenosina Trifosfato/metabolismo , Alelos , Secuencia de Aminoácidos , Arabidopsis/efectos de los fármacos , Arabidopsis/crecimiento & desarrollo , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Fraccionamiento Celular , Regulación de la Expresión Génica de las Plantas , Genes de Plantas , Prueba de Complementación Genética , Sitios Genéticos , Células Germinativas de las Plantas/citología , Células Germinativas de las Plantas/metabolismo , Histonas/genética , Histonas/metabolismo , Immunoblotting , Mitomicina/farmacología , Datos de Secuencia Molecular , Mutagénesis Sitio-Dirigida , Fenotipo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Polen/genética , Polen/metabolismo , Complejo de la Endopetidasa Proteasomal/genética , Eliminación de Secuencia , Transducción de Señal , TransgenesRESUMEN
The biosynthetic gene cluster of brassicicene C was identified in Alternaria brassicicola strain ATCC 96836 from genome database search. In vivo and in vitro study clearly revealed the function of Orf8 and Orf6 as a fusicoccadiene synthase and methyltransferase, respectively. The understanding toward the biosynthetic pathway promises construction of this type of diterpene compounds with genetic engineering.