Zinc knuckle (ZCCHC) motif-containing proteins are present in unicellular and multicellular eukaryotes, and most ZCCHC proteins with known functions participate in the metabolism of various classes of RNA, such as mRNAs, ribosomal RNAs, and microRNAs. The Arabidopsis (Arabidopsis thaliana) genome encodes 69 ZCCHC-containing proteins; however, the functions of most remain unclear. One of these proteins, CAX-INTERACTING PROTEIN 4 (CXIP4, encoded by AT2G28910), has been classified as a PTHR31437 family member. This family includes human Splicing regulatory glutamine/lysine-rich protein 1 (SREK1)-interacting protein 1 (SREK1IP1), which is thought to function in pre-mRNA splicing and RNA methylation. Metazoan SREK1IP1-like and plant CXIP4-like proteins only share a ZCCHC motif, and their functions remain almost entirely unknown. Here, we studied two loss-of-function alleles of Arabidopsis CXIP4: cxip4-1 is likely null and shows early lethality, and cxip4-2 is hypomorphic and viable, with pleiotropic morphological defects. The cxip4-2 mutant exhibited deregulation of defense genes and upregulation of transcription factor genes, some of which might explain its developmental defects. The cxip4-2 mutant also exhibited increased intron retention events, being more evident in cxip4-1. The specific functions of misspliced genes, such as those involved in “gene silencing by DNA methylation” and “mRNA polyadenylation factor” suggest that CXIP4 has additional functions. In cxip4-2 plants, polyadenylated RNAs accumulate in the nucleus; these could be misspliced mRNAs. The CXIP4 protein localizes to the nucleus in a pattern resembling nuclear speckles rich in splicing factors. Therefore, CXIP4 is required for plant development and survival and mRNA maturation.

The growing demand for sustainable alternatives to non-renewable growing media components, such as sphagnum peat, has driven interest in compost–biochar combinations as high-quality horticultural substrates. Nevertheless, the effects of incorporating biochar at the onset of co-composting on process dynamics and the quality of the resulting end-products remain poorly understood and insufficiently characterized. This study evaluated the influence of hardwood residue-derived biochar as an additive on the co-composting of corn stover and swine manure under greenhouse conditions over 94 days. Three treatments were established: a Control (C; without biochar), CB1 (10% v/v biochar), and CB2 (20% v/v biochar), each with three replicates. Physicochemical properties (pH, electrical conductivity, water holding capacity, bulk density, particle size distribution, total organic carbon), enzyme activities (FDA hydrolysis, dehydrogenase, urease, arginine ammonification, acid phosphatase, arylsulfatase), compost stability (Solvita^® test), and phytotoxicity (germination index) were monitored throughout the process and at process completion. Results showed that biochar addition significantly influenced physicochemical and biological parameters in a dose-dependent manner. The CB2 treatment reduced electrical conductivity by 46% relative to the Control (1.87 vs. 3.45 mS/cm) and increased water-holding capacity by 32% (479 vs. 364%), while all treatments met the Chilean composting standard NCh 2880. Enzyme activities were generally higher in the Control and CB1 treatments, indicating that high biochar rates may limit microbial activity due to recalcitrant carbon inputs, yet a 20% biochar addition improved compost maturity and reduced phytotoxicity. These findings indicate that, within the tested range (10–20% v/v), biochar incorporation appears to enhance the quality, supporting its potential as a sustainable component in growing media formulations as an alternative to peat.

Zinc knuckle (ZCCHC) motif-containing proteins are present in unicellular and multicellular eukaryotes and most ZCCHC proteins with known functions participate in the metabolism of various classes of RNA, such as mRNAs, ribosomal RNAs, and microRNAs. The Arabidopsis ( Arabidopsis thaliana ) genome encodes 69 ZCCHC-containing proteins, but the functions of most remain unclear. One of these proteins is CAX-INTERACTING PROTEIN 4 (CXIP4), which has been classified as a PTHR31437 family member, along with human SREK1-interacting protein 1 (SREK1IP1), which is thought to function in pre-mRNA splicing and RNA methylation. Metazoan SREK1IP1-like and plant CXIP4-like proteins only share a ZCCHC motif, and their functions remain almost entirely unknown. We studied two loss-of-function alleles of Arabidopsis CXIP4 , the first mutations in PTHR31437 family genes described to date: cxip4-1 is likely null and shows early lethality, and cxip4-2 is hypomorphic and viable, with pleiotropic morphological defects. The cxip4-2 mutant exhibited deregulation of defense genes and upregulation of transcription factor encoding genes, some of which might explain its developmental defects. This mutant also exhibited increased intron retention events, and the specific functions of misspliced genes, such as those involved in “gene silencing by DNA methylation” and “mRNA polyadenylation factor” suggest that CXIP4 has additional functions. The CXIP4 protein localizes to the nucleus in a pattern resembling nuclear speckles, which are rich in splicing factors. Therefore, CXIP4 is required for plant survival and proper development, and mRNA maturation.