RESUMEN
We previously identified three glycosylphosphatidylinositol (GPI)-anchored proteins including Ecm33, as multicopy suppressors of the phenotypes of a mutant allele of cis4(+) that encodes a zinc transporter in fission yeast. Here, we further identified two multicopy suppressor genes, ubi1 (+) and ubc4 (+), encoding ubiquitin-ribosomal fusion protein and ubiquitin conjugating enzyme E2, respectively. In addition, Ubi1 or Ubc4 overexpression failed to suppress the phenotypes of the double deletion of cis4 (+) and pub1 (+) gene, which encodes a HECT-type ubiquitin ligase E3. During exponential phase GFP-Ecm33 localized at the growing cell tips of the cell surface and the medial region in wild-type cells. Notably, during the post-exponential and stationary phase, GFP-Ecm33 in wild-type cells was internalized and mostly localized to the Golgi/endosomes, but it was still stably localized at the cell surface in Δpub1 cells. The Δpub1 cells showed osomoremedial phenotypes to various drugs indicating their defects in cell wall integrity. Altogether, our findings reveal a novel role for Pub1 in endocytosis of Ecm33 and regulation of cell wall integrity in fission yeast.
Asunto(s)
Ligasas de Carbono-Nitrógeno/metabolismo , Endocitosis , Pleiotropía Genética/efectos de la radiación , Proteínas de la Membrana/metabolismo , Proteínas de Schizosaccharomyces pombe/metabolismo , Schizosaccharomyces/citología , Schizosaccharomyces/metabolismo , Calcineurina/metabolismo , Pared Celular/metabolismo , Proteínas de la Membrana/genética , Mutación , Elementos de Respuesta/genética , Schizosaccharomyces/genética , Proteínas de Schizosaccharomyces pombe/genética , Transcripción Genética , Enzimas Ubiquitina-Conjugadoras/genética , Enzimas Ubiquitina-Conjugadoras/metabolismoRESUMEN
BACKGROUND AND AIMS: Plants growing at high densities perceive a decrease in the red to far-red (R/FR) ratio of incoming light. These changes in light quality trigger a suite of responses collectively known as the shade-avoidance syndrome (SAS) including hypocotyl and stem elongation, inhibition of branching and acceleration of flowering. METHODS: Quantitative trait loci (QTLs) were mapped for hypocotyl length to end-of-day far-red (EOD), a simulated shade-avoidance response, in recombinant inbred line (RIL) populations of Arabidopsis thaliana seedlings, derived from Landsberg erecta (Ler) and three accessions (Columbia, Col; Nossen, No-0; and Cape Verde Islands, Cvi-0). KEY RESULTS: Five loci were identified as being responsible for the EOD response, with a positive contribution of Ler alleles on the phenotype independently of the RIL population. Quantitative complementation analysis and transgenic lines showed that PHYB is the candidate gene for EODRATIO5 in the Ler × Cvi-0 RIL population, but not for two co-localized QTLs, EODRATIO1 and EODRATIO2 mapped in the Ler × No-0 and Ler × Col RIL populations, respectively. The ERECTA gene was also implicated in the SAS in a background-dependent manner. For hypocotyl length EOD response, a positive contribution of erecta alleles was found in Col and Van-0, but not in Ler, Cvi-0, Hir-1 or Ws. Furthermore, pleiotropic effects of ERECTA in the EOD response were also detected for petiole and lamina elongation, hyponastic growth, and flowering time. CONCLUSIONS: The results show that the analysis of multiple mapping populations leads to a better understanding of the SAS genetic architecture. Moreover, the background- and trait-dependent contribution of ERECTA in the SAS suggest that its function in shaded natural environments may be relevant for some populations in different phases of plant development. It is proposed that ERECTA is involved in canalization processes buffering the genetic variation of the SAS against environmental light fluctuations.
Asunto(s)
Proteínas de Arabidopsis/metabolismo , Arabidopsis/enzimología , Arabidopsis/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Receptores de Superficie Celular/metabolismo , Arabidopsis/genética , Arabidopsis/efectos de la radiación , Proteínas de Arabidopsis/genética , Emparejamiento Base/genética , Cromosomas de las Plantas/genética , Ecotipo , Estudios de Asociación Genética , Pleiotropía Genética/efectos de la radiación , Variación Genética/efectos de la radiación , Genotipo , Hipocótilo/crecimiento & desarrollo , Hipocótilo/efectos de la radiación , Endogamia , Luz , Fitocromo B/genética , Proteínas Serina-Treonina Quinasas/genética , Sitios de Carácter Cuantitativo/genética , Carácter Cuantitativo Heredable , Receptores de Superficie Celular/genéticaRESUMEN
Phytochrome B (phyB), a major photoreceptor in plants, interacts with transcription factors to regulate gene expression and induce various light responses. Recently, we identified an SR-like splicing factor, RRC1 (reduced red-light responses in cry1cry2 background 1), as a novel component of phyB signaling in Arabidopsis. RRC1 has a C-terminal arginine/serine-rich (RS) domain that is generally important for the regulation of alternative splicing. Whereas rrc1 hypomorphic mutant alleles produce truncated RRC1 proteins that lack the C-terminal region, including the RS domain, and exhibit splicing defects and reduced phyB signaling, the rrc1-4 null allele additionally displays pleiotropic developmental abnormalities with more severe splicing defects. Here, we show that transgenic Arabidopsis plants that express truncated RRC1 lacking the RS domain in the rrc1-4 null allele background exhibited the same phenotype as the hypomorphic alleles. Hence, we conclude that deletion of the RS domain of RRC1 reduces phyB signaling, probably due to aberrant regulation of alternative splicing of target genes.
Asunto(s)
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Fitocromo B/metabolismo , Eliminación de Secuencia , Transducción de Señal , Arabidopsis/crecimiento & desarrollo , Arabidopsis/efectos de la radiación , Pleiotropía Genética/efectos de la radiación , Hipocótilo/crecimiento & desarrollo , Hipocótilo/metabolismo , Hipocótilo/efectos de la radiación , Luz , Mutación/genética , Estructura Terciaria de Proteína , Transducción de Señal/efectos de la radiación , Relación Estructura-ActividadRESUMEN
The chloroplast is the site of photosynthesis in higher plants but also functions as the center of synthesis for primary and specialized metabolites including amino acids, fatty acids, starch, and diverse isoprenoids. Mutants that disrupt aspects of chloroplast function represent valuable tools for defining structural and biochemical regulation of the chloroplast and its interplay with whole-plant structure and function. The lutescent1 (l1) and l2 mutants of tomato (Solanum lycopersicum) possess a range of chlorophyll-deficient phenotypes including reduced rates of chlorophyll synthesis during deetiolation and enhanced rates of chlorophyll loss in leaves and fruits as they age, particularly in response to high-light stress and darkness. In addition, the onset of fruit ripening is delayed in lutescent mutants by approximately 1 week although once ripening is initiated they ripen at a normal rate and accumulation of carotenoids is not impaired. The l2 locus was mapped to the long arm of chromosome 10 and positional cloning revealed the existence of a premature stop codon in a chloroplast-targeted zinc metalloprotease of the M50 family that is homologous to the Arabidopsis (Arabidopsis thaliana) gene ETHYLENE-DEPENDENT GRAVITROPISM DEFICIENT AND YELLOW-GREEN1. Screening of tomato germplasm identified two additional l2 mutant alleles. This study suggests a role for the chloroplast in mediating the onset of fruit ripening in tomato and indicates that chromoplast development in fruit does not depend on functional chloroplasts.