Effects of ion beam irradiation on morphological and flowering characteristics of chrysanthemum

Chrysanthemum morifolium is an important temperate cut flower for Malaysian floriculture industry and the lack of new local owned varieties led to this mutation breeding research. The objective of this study was to compare the effectiveness of ion beam irradiation in generating mutations on ray florets and nodal explants of Chrysanthemum morifolium cv. ‘Reagan Red’. Ion beams has become an efficient physical mutagen for mutation breeding. The ray florets and nodal explants were irradiated with ion beams at doses 0, 0.5, 1.0, 2.0, 3.0, 5.0, 8.0, 10, 15, 20 and 30 Gy. The 50% of in vitro shoot regeneration (RD50) for ray florets explants was 2.0 Gy and for nodal explants was 4.0 Gy. Thus, relative biological effectiveness (RBE) for ray florets was found 2.0 times higher than the nodal explants. The regenerated plantlets were planted in the greenhouse at MARDI, Cameron Highlands for morphological screening. Overall performance of survival plantlets derived from in vitro nodal and ray floret explants was recorded. The characters studied include plant morphology and flowering characteristic. The ray florets explants were found to be more sensitive to ion beam irradiation and generated more mutations as compared to nodal explants

Yokonolide B, a Novel Inhibitor of Auxin Action, Blocks Degradation of AUX/IAA Factors

Yokonolide B (YkB; also known as A82548A), a spiroketal-macrolide, was isolated from Streptomyces diastatochromogenes B59 in a screen for inhibitors of beta-glucoronidase expression under the control of an auxin-responsive promoter in Arabidopsis. YkB inhibits the expression of auxin-inducible genes as shown using native and synthetic auxin promoters as well as using expression profiling of 8300 Arabidopsis gene probes but does not affect expression of an abscisic acid- and a gibberellin A3-inducible gene. The mechanism of action of YkB is to block AUX/IAA protein degradation; however, YkB is not a general proteasome inhibitor. YkB blocks auxin-dependent cell division and auxin-regulated epinastic growth mediated by auxin-binding protein 1. Gain of function mutants such as shy2-2, slr1, and axr2-1 encoding AUX/IAA transcriptional repressors and loss of function mutants encoding components of the ubiquitin-proteolytic pathway such as axr1-3 and tir1-1, which display increased AUX/IAAs protein stability, are less sensitive to YkB, although axr1 and tir1 mutants were sensitive to MG132, a general proteasome inhibitor, consistent with a site of action downstream of AXR1 and TIR. YkB-treated seedlings displayed similar phenotypes as dominant AUX/IAA mutants. Taken together, these results indicate that YkB acts to block AUX/IAA protein degradation upstream of AXR and TIR, links a shared element upstream of AUX/IAA protein stability to auxin-induced cell division/elongation and to auxin-binding protein 1, and provides a new tool to dissect auxin signal transduction

Construction of Mutant Lines of the Parasitic Plant Cuscuta campestris Yuncker by Carbon Ion Irradiation, and Development of an in vitro System for Screening

Cuscuta species is one of the most widespread group of parasitic plants that subsists on various plant species, causing damages to important crops. Cuscuta species absorbs water and nutrients from host plants through an invasive organ called a haustorium. Understanding the molecular basis of the invasive processes of Cuscuta species is of critical importance to crop production. In this work, we establish high-throughput screening assays for parasitism mutants in C. campestris

Detection of Somatic Mutations in Plant DNA by the Maximum-Depth Sequencing

Radiation-induced mutagenesis is a powerful tool for generating mutants in plant biology. However, there is no quick and direct methods to evaluate radiation dose suitable for inducing mutations. In this work, we tried maximum-depth sequencing (MDS), a method that can detect extremely rare mutations in a population of cells through next generation sequencing (NGS) with error correction, to detect locus-specific somatic mutations in gamma-irradiated Arabidopsis plants

Effects of carbon ion beam-induced mutagenesis for the screening of RED production-deficient mutants of Streptomyces coelicolor JCM4020.

Streptomyces lividans TK23 interacts with mycolic acid-containing bacteria (MACB), such as Tsukamurella pulmonis TP-B0596, and this direct cell contact activates its secondary metabolism (e.g., the production of undecylprodigiosin: RED). Here, we employed carbon (12C5+) ion beam-induced mutagenesis to investigate the signature of induced point mutations and further identify the gene(s) responsible for the production of secondary metabolites induced by T. pulmonis. We irradiated spores of the Streptomyces coelicolor strain JCM4020 with carbon ions to generate a mutant library. We screened the RED production-deficient mutants of S. coelicolor by mixing them with T. pulmonis TP-B0596 on agar plates, identifying the red/white phenotype of the growing colonies. Through this process, we selected 59 RED-deficient mutants from around 152,000 tested spores. We resequenced the genomes of 16 mutants and identified 44 point mutations, which revealed the signatures induced by 12C5+-irradiation. Via gene complementation experiments, we also revealed that two genes-glutamate synthase (gltB) and elongation factor G (fusA)-are responsible for the reduced production of RED

Characterization of Cuscuta campestris cell wall genes responsible for the haustorial invasion of host plants

Cuscuta is one of the most widespread genera of parasitic plants that subsist on various types of herbaceous angiosperms. Since their hosts include economically important crops, understanding the molecular basis of parasitism in Cuscuta species is critical for crop production. Despite the advances in biology and agriculture, the mechanisms of host plant infection by parasitic plants remain largely unknown. To gain insight into the mechanism of parasitism, we focused on Cuscuta campestris genes encoding enzymes involved in the degradation and modification of host cell walls, and characterized their expression during haustorial invasion. Analysis of previously published RNA-seq data showed that certain genes encoding pectin methylesterases, polygalacturonases, and cellulosecellulase-like enzymes were correlated with the haustorial invasion of host tissues. These data confirm that haustorial invasion by Cuscuta species is facilitated not only by mechanical action but also by the specific biochemical degradation and modification of host cell walls.Keywords: Parasitic plant, haustorium, cell wall, gene family, CAZym