Chloroplast gene expression relies on nucleus-encoded factors for RNA metabolism processing, but the mechanisms under cold stress remain poorly understood.  In this study, we isolated and characterized a foxtail millet (Setaria italica) mutant, temperature-sensitive chlorophyll-deficient (sitcd1), which exhibited reduced chlorophyll content and abnormal chloroplasts, resulting in an albino phenotype during early leaf development at low temperatures (20°C during the day and 18°C at night).  Map-based cloning revealed that SiTCD1 encoded a P-type PPR protein localized in chloroplasts.  In sitcd1 background, transgenic lines of SiTCD1 overexpression appeared nearly normal green leaves under L20/D18 condition.  SiTCD1 was especially expressed in earlier development of leaves under low temperature.  Additionally, SiTCD1 directly bound to the plastid gene atpF in vitro, which might participate in the splicing of plastid gene atpF under low temperature.  RNA-seq indicated that the expression of genes related to metabolism (such as porphyrin, chlorophyll and glutathione metabolism), which required ATP for energy, was down-regulated in sitcd1, resulting in decreased chlorophyll content, GSH, and its redox couple (GSH/GSSG) at low temperature.  As sitcd1 exhibited more sensitive at the bud bursting stage than germination and seedling stage under cold stress, we identified two haplotypes of SiTCD1 (SiTCD1^Hap1 and SiTCD1^Hap2) in 195 accessions, and found that accessions carrying the SiTCD1^Hap2 allele were more tolerant to cold stress than those with the SiTCD1^Hap1 allele at the bud bursting stage.  In summary, our results suggest that SiTCD1 is essential for early chloroplast development under low temperature in foxtail millet.

The rice planthopper, Sogatella furcifera, is a piercing-sucking insect pest of rice, Oryza sativa.  It is responsible for significant crop yield losses, and has developed moderate to high resistance to several commonly used chemical insecticides.  We investigated the effects of the insect fungal pathogen Isaria javanica, alone and in combination with the chemical insecticide dinotefuran, on S. furcifera under both laboratory and field conditions.  Our results show that I. javanica displays high infection efficiency and mortality for different stages of S. furcifera, reducing adult survival, female oviposition and ovary development.  Laboratory bioassays showed that the combined use of I. javanica with a low dose (4–16 mg L^–1) of dinotefuran resulted in higher mortality in S. furcifera than the use of I. javanica or dinotefuran alone.  The combined treatment also had more significant effects on several host enzymes, including superoxide dismutase, catalase, peroxidase, and prophenol oxidase activities.  In field trials, I. javanica effectively suppressed populations of rice planthoppers to low levels (22–64% of the level in untreated plots).  Additional field experiments showed synergistic effects, i.e., enhanced efficiency, for the control of S. furcifera populations using the combination of a low dose of I. javanica (1×10⁴ conidia mL^–1) and a low dose of dinotefuran (~4.8–19.2% of normal field use levels), with control effects of >90% and a population level under 50 insects per 100 hills at 3–14 days post-treatment.  Our findings indicate that the entomogenous fungus I. javanica offers an attractive biological control addition as part of the integrated pest management (IPM) practices for the control of rice plant pests.