Background
Chloroplast development is coordinately regulated by plastid- and nuclear-encoding genes. Although many regulators have been reported to be involved in chloroplast development, new factors remain to be identified, given the complexity of this process.
Results
In this study, we characterized a rice mutant
lethal albinic seedling 1
(
las1
)form of a 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (OsHMBPP) that was targeted to the chloroplasts. The
LAS1
mutation caused the albino lethal phenotype in seedlings. Transmission electron microscopy indicated that
las1
were defective in early chloroplast development.
LAS1
is preferentially expressed in leaves, implying its role in controlling chloroplast development. The expression levels of many chloroplast-encoded genes were altered significantly in
las1
. The expression levels of nuclear-encoded gene involved in Chl biosynthesis were also decreased in
las1
. We further investigated plastidic RNA editing in
las1
and found that the edit efficiency of four chloroplast genes were markly altered. Compared with WT,
las1
exhibited defective in biogenesis of chloroplast ribosomes.
Conclusions
Our results show that
LAS1/OsHMBPP
plays an essential role in the early chloroplast development in rice.
Background
Plant plastidic caseinolytic protease (Clp) is a central part of the plastid protease network and consists of multiple subunits. The molecular functions of many Clps in plants, especially in crops, are not well known.
Results
In this study, we identified an albino lethal mutant al3 in rice, which produces albino leaves and dies at the seedling stage. Molecular cloning revealed that AL3 encodes a plastid caseinolytic protease, OsClpR1, homologous to Arabidopsis ClpR1 and is targeted to the chloroplast. Compared with the wild type, chloroplast structure in the al3 mutant was poorly developed. OsClpR1 was constitutively expressed in all rice tissues, especially in young leaves. The OsClpR1 mutation affected the transcript levels of chlorophyll biosynthesis and chloroplast development-related genes. The RNA editing efficiency of three chloroplast genes (rpl2, ndhB, ndhA) was remarkably reduced in al3. Using a yeast two-hybrid screen, we found that OsClpR1 interacted with OsClpP4, OsClpP5, OsClpP2, and OsClpS1.
Conclusions
Collectively, our results provide novel insights into the function of Clps in rice.
Chrysanthemum Fusarium wilt is a soil-borne disease that causes serious economic losses to the chrysanthemum industry. However, the molecular mechanism underlying the response of chrysanthemum WRKY to Fusarium oxysporum infection remains largely unknown. In this study, we isolated CmWRKY6-1 from chrysanthemum ‘Jinba’ and identified it as a transcriptional repressor localized in the nucleus via subcellular localization and transcriptional activation assays. We found that CmWRKY6-1 negatively regulated resistance to F. oxysporum and affected reactive oxygen species (ROS) and salicylic acid (SA) pathways using transgenic experiments and transcriptomic analysis. Moreover, CmWRKY6-1 bound to the W-box element on the CmWRKY15-like promoter and inhibited its expression. Additionally, we observed that CmWRKY15-like silencing in chrysanthemum reduced its resistance to F. oxysporum via transgenic experiments. In conclusion, we revealed the mechanism underlying the CmWRKY6-1–CmWRKY15-like cascade response to F. oxysporum infection in chrysanthemum and demonstrated that CmWRKY6-1 and CmWRKY15-like regulates the immune system.
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