Cell cycle-dependent phosphorylation of pRb-like protein in root meristem cells of Vicia faba

The retinoblastoma tumor suppressor protein (pRb) regulates cell cycle progression by controlling the G1-to-S phase transition. As evidenced in mammals, pRb has three functionally distinct binding domains and interacts with a number of proteins including the E2F family of transcription factors, proteins with a conserved LxCxE motif (D-type cyclin), and c-Abl tyrosine kinase. CDK-mediated phosphorylation of pRb inhibits its ability to bind target proteins, thus enabling further progression of the cell cycle. As yet, the roles of pRb and pRb-binding factors have not been well characterized in plants. By using antibody which specifically recognizes phosphorylated serines (S807/811) in the c-Abl tyrosine kinase binding C-domain of human pRb, we provide evidence for the cell cycle-dependent changes in pRb-like proteins in root meristems cells of Vicia faba. An increased phosphorylation of this protein has been found correlated with the G1-to-S phase transition

First Report of <i>Tomato yellow leaf curl virus</i> Co-infecting Pepper with <i>Tomato chino La Paz virus</i> in Baja California Sur, Mexico

Chile peppers are among the most common and important crops in the State of Baja California Sur, Mexico, where diverse varieties of this crop are annually cultivated. The “chile ancho” (Capsicum annuum L. var. ancho poblano) is one of the most popular hot peppers that is exported fresh to the United States. During a survey in December of 2007 in an experimental field of the CIBNOR in El Carrizal, one of the principal farm districts in the state, a high incidence of yellowing, stunted growth with shortened internodes, foliage discoloration, malformation and crinkle, abortion of flowers, and reduction in size and quantity of fruit were noted in chile ancho. Symptoms and the presence of large populations of whiteflies in the field suggested a possible viral etiology of disease. The symptoms of disease were successfully transmitted by grafting from field plants to tomato and pepper test plants. Samples from both field and test plants were analyzed by scanning electron microscopy (SEM) and molecular techniques. SEM study revealed groups of geminate particles characteristic of begomoviruses (Geminiviridae) in phloem tissue of randomly selected symptomatic plants (four field and two test plants). Total DNA from 12 symptomatic plants (eight naturally infected and four test plants) was obtained by a modified Dellaporta method and analyzed by PCR using the begomovirus universal primers prRepDGR (2) and prC889 (3). Amplicons of ~1.4 kb were obtained from all plant samples and PCR products from four of them were cloned into pGEM-T Easy vector (Promega, Madison, WI) and subsequently analyzed by restriction fragment length polymorphism (RFLP) using EcoRI and HinfI. Two distinct restriction fragment patterns were observed among the cloned PCR products, indicating the occurrence of at least two viruses in the infected plant tissues. The four examined samples contained the same two begomoviruses according to the RFLP analysis data. The complete sequence of the genomic component A of those viruses was determined by PCR amplification of viral DNA with universal, degenerate primers previously described (2), the subsequent cloning of overlapped PCR products, and sequencing. The full-length DNA-A sequence was assembled and compared with viral sequences available at the GenBank database using BlastN and the ClustalV alignment method (MegAlign; DNASTAR, Madison, WI). The 2,781-bp complete genome sequence of one co-infecting monopartite begomovirus (Accession No. HM459851) displayed the highest identity (99%) with Tomato yellow leaf curl virus (TYLCV), isolate Guasave, Sinaloa (Accession No. FJ609655). The 2,609-bp DNA-A sequence of the second begomovirus exhibited the highest nucleotide identity (96%) with Tomato chino La Paz virus (ToChLPV)-[Baja California Sur] (Accession No. AY339619). The presence of TYLCV in this region of Mexico had not been previously reported nor was ToChLPV detected in pepper until now. To our knowledge, this is the first report of a mixed infection of pepper plants with TYLCV and a bipartite begomovirus in Baja California Peninsula. Since the high frequency of recombination events observed in begomovirus mixed infections involving TYLCV (1), it would be important to monitor the possible emergence of ToChLPV-TYLCV recombinants with higher potential virulence. References: (1) S. García-Andrés et al. Virology 365:210, 2007. (2) A. Mauricio-Castillo et al. Plant Dis. 91:1513, 2007. (3) S. D. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996. </jats:p

Enhanced Tissue-Specific Expression of the Herbicide Resistance bar Gene in Transgenic Cotton (Gossypium hirsutum L cv. Coker 310FR) Using the Arabidopsis rbcS ats1A Promoter

A highly regenerating cotton (Gossypium hirsutum L.) cultivar, Coker 310FR, was used to generate transgenic plants expressing the herbicide resistance gene, bar, encoding phosphinothricin acetyltransferase (PAT), under the transcriptional control of the ribulose-1, 5-bisphosphate carboxylase (Rubisco) small subunit (rbcS) ats1A gene promoter from Arabidopsis thaliana. Expression levels of the rbcS ats1A-bar transgenes were compared to bar transgenes under the control of the high level constitutive promoter from the Cauliflower Mosaic Virus 35S gene containing a dual enhancer region (2xE CaMV 35S). Significantly higher levels of bar mRNA, PAT protein and enzymatic activity, and enhanced levels of resistance to the herbicide Basta were observed in transgenic plants expressing bar under the rbcS ats1A promoter compared to the 2xE CaMV 35S promoter. Transgenic plants containing 2xE CaMV 35S-bar transgenes tolerated the maximum herbicide (Basta) application up to 200 mg PPT whereas rbcS ats1A-bar transgenic plants were capable of detoxifying Basta up to 400 mg l-1 PPT. These findings indicate that the rbcS ats1A promoter may be useful for higher expression of transgenes in developing tissues of cotton for improving it further through genetic engineering