The spliceophilin CYP18-2 is mainly involved in the splicing of retained introns under heat stress in Arabidopsis

Peptidyl-prolyl isomerase-like 1(PPIL1)is associated with the human spliceosome complex.However,its function in pre-mRNA splicing remains unclear.In this study,we show that Arabidopsis thaliana CYCLOPHILIN 18-2(AtCYP18-2),a PPIL1 homolog,plays an essential role in heat tolerance by regulating pre-mRNA splicing.Under heat stress conditions,AtCYP18-2 expression was upregulated in mature plants and GFP-tagged AtCYP18-2 redistributed to nuclear and cytoplasmic puncta.We determined that AtCYP18-2 interacts with several spliceosome complex B^(ACT)components in nuclear puncta and is primarily associated with the small nuclear RNAs U5 and U6 in response to heat stress.The AtCYP18-2 loss-of-function allele cyp18-2 engineered by CRISPR/Cas9-mediated gene editing exhibited a hypersensitive phenotype to heat stress relative to the wild type.Moreover,global transcriptome profiling showed that the cyp18-2 mutation affects alternative splicing of heat stress–responsive genes under heat stress conditions,particularly intron retention(IR).The abundance of most intron-containing transcripts of a subset of genes essential for thermotolerance decreased in cyp18-2 compared to the wild type.Furthermore,the intron-containing transcripts of two heat stress-related genes,HEAT SHOCK PROTEIN 101(HSP101)and HEAT SHOCK FACTOR A2(HSFA2),produced functional proteins.HSP101-IR-GFP localization was responsive to heat stress,and HSFA2-Ⅲ-IR interacted with HSF1 and HSP90.1 in plant cells.Our findings reveal that CYP18-2 functions as a splicing factor within the B~(ACT)spliceosome complex and is crucial for ensuring the production of adequate levels of alternatively spliced transcripts to enhance thermotolerance.

Lattice Preferred Orientation, Water Content, and Seismic Anisotropy of Orthopyroxene

Lattice preferred orientation （LPO） and seismic anisotropy of orthopyroxene （enstatite） in mantle xenoliths from Spitsbergen, Svalbard, near the Arctic, are studied. LPOs of enstatite were determined using electron backseattered diffraction （EBSD）. We found four types of LPOs of orthopyroxene and defined them as type-AC, -AB, -BC, and -ABC. Type-AC LPO of orthopyroxene is defined as （100） plane aligned subparallel to foliation and [001] axis aligned subparallel to lineation. Type-AB LPO is defined as （100） plane aligned subparallel to foliation and [010] axis aligned subparallel to linea- tion. Type-BC LPO is defined as （010） plane aligned subparallel to foliation and [001] axis aligned subparallel to lineation. Type-ABC LPO is defined as both （100） and （010） planes aligned subparallel to foliation with a girdle distribution of both [100] and [010] axes normal to lineation and [001] axis aligned subparallel to lineation. We report for the first time the type-AB, -BC, and -ABC LPO of orthopyroxerie. We found that the LPO pattern has a correlation with the content of orthopyroxene in the specimen. Nicolet 6700 FTIR （Fourier transformation infrared） study of enstatite showed that type-AC LPO was observed mostly in the samples of enstatite with low water content. It is found that the strength of the LPO of enstatite decreases with increasing water content and has a correlation with the strength of the LPO of olivine： the stronger the LPO of enstatite, the stronger the LPO of olivine. Seismic anisotropy of enstatite was smaller than that of olivine in the same specimen.