32 research outputs found
Silencing COI1 in Rice Increases Susceptibility to Chewing Insects and Impairs Inducible Defense
The jasmonic acid (JA) pathway plays a key role in plant defense responses against herbivorous insects. CORONATINE INSENSITIVE1 (COI1) is an F-box protein essential for all jasmonate responses. However, the precise defense function of COI1 in monocotyledonous plants, especially in rice (Oryza sativa L.) is largely unknown. We silenced OsCOI1 in rice plants via RNA interference (RNAi) to determine the role of OsCOI1 in rice defense against rice leaf folder (LF) Cnaphalocrocis medinalis, a chewing insect, and brown planthopper (BPH) Nilaparvata lugens, a phloem-feeding insect. In wild-type rice plants (WT), the transcripts of OsCOI1 were strongly and continuously up-regulated by LF infestation and methyl jasmonate (MeJA) treatment, but not by BPH infestation. The abundance of trypsin protease inhibitor (TrypPI), and the enzymatic activities of polyphenol oxidase (PPO) and peroxidase (POD) were enhanced in response to both LF and BPH infestation, but the activity of lipoxygenase (LOX) was only induced by LF. The RNAi lines with repressed expression of OsCOI1 showed reduced resistance against LF, but no change against BPH. Silencing OsCOI1 did not alter LF-induced LOX activity and JA content, but it led to a reduction in the TrypPI content, POD and PPO activity by 62.3%, 48.5% and 27.2%, respectively. In addition, MeJA-induced TrypPI and POD activity were reduced by 57.2% and 48.2% in OsCOI1 RNAi plants. These results suggest that OsCOI1 is an indispensable signaling component, controlling JA-regulated defense against chewing insect (LF) in rice plants, and COI1 is also required for induction of TrypPI, POD and PPO in rice defense response to LF infestation
The wheat stem rust resistance gene Sr43 encodes an unusual protein kinase
To safeguard bread wheat against pests and diseases, breeders have
introduced over 200 resistance genes into its genome, thus nearly doubling
the number of designated resistance genes in the wheat gene pool1. Isolating
these genes facilitates their fast-tracking in breeding programs and
incorporation into polygene stacks for more durable resistance. We cloned
the stem rust resistance gene Sr43, which was crossed into bread wheat from
the wild grass Thinopyrum elongatum2,3. Sr43 encodes an active protein kinase
fused to two domains of unknown function. The gene, which is unique to the
Triticeae, appears to have arisen through a gene fusion event 6.7 to 11.6 million
years ago. Transgenic expression of Sr43 in wheat conferred high levels of
resistance to a wide range of isolates of the pathogen causing stem rust,
highlighting the potential value of Sr43 in resistance breeding and engineering
The peroxisome: still a mysterious organelle
More than half a century of research on peroxisomes has revealed unique features of this ubiquitous subcellular organelle, which have often been in disagreement with existing dogmas in cell biology. About 50 peroxisomal enzymes have so far been identified, which contribute to several crucial metabolic processes such as β-oxidation of fatty acids, biosynthesis of ether phospholipids and metabolism of reactive oxygen species, and render peroxisomes indispensable for human health and development. It became obvious that peroxisomes are highly dynamic organelles that rapidly assemble, multiply and degrade in response to metabolic needs. However, many aspects of peroxisome biology are still mysterious. This review addresses recent exciting discoveries on the biogenesis, formation and degradation of peroxisomes, on peroxisomal dynamics and division, as well as on the interaction and cross talk of peroxisomes with other subcellular compartments. Furthermore, recent advances on the role of peroxisomes in medicine and in the identification of novel peroxisomal proteins are discussed
AtCCMH, an essential component of the c-type cytochrome maturation pathway in Arabidopsis mitochondria, interacts with apocytochrome c
The maturation of c-type cytochromes requires the covalent ligation of the heme cofactor to reduced cysteines of the CXXCH motif of apocytochromes. In contrast to mitochondria of other eukaryotes, plant mitochondria follow a pathway close to that found in α- and γ-proteobacteria. We identified a nuclear-encoded protein, AtCCMH, the Arabidopsis thaliana ortholog of bacterial CcmH/CycL proteins. In bacteria, CcmH and the thioredoxin CcmG are components of a periplasmic thio-reduction pathway proposed to maintain the apocytochrome c cysteines in a reduced state. AtCCMH is located exclusively in mitochondria. AtCCMH is an integral protein of the inner membrane with the conserved RCXXC motif facing the intermembrane space. Reduction assays show that the cysteine thiols in the RCXXC motif of AtCCMH can form a disulfide bond that can be reduced by enzymatic thiol reductants. A reduced form of AtCCMH can reduce the intra-disulfide bridge of a model peptide of apocytochrome c. When expressed in Escherichia coli, AtCCMH coimmunoprecipitates with the bacterial CcmF, a proposed component of the heme lyase. Blue-native PAGE of mitochondrial membrane complexes reveals the colocalization of AtCCMH and AtCcmF(N2) in a 500-kDa complex. Yeast two-hybrid assays show an interaction between the AtCCMH intermembrane space domain and A. thaliana apocytochrome c. A. thaliana ccmh/ccmh knockout plants show lethality at the torpedo stage of embryogenesis. Our results show that AtCCMH is an essential mitochondrial protein with characteristics consistent with its proposed apocytochrome c-reducing and heme lyase function