Changes in mRNA Degradation Efficiencies under Varying Conditions Are Regulated by Multiple Determinants in Arabidopsis thaliana.

Multiple mechanisms are involved in gene expression, with mRNA degradation being critical for the control of mRNA accumulation. In plants, although some trans-acting factors and motif sequences have been identified in deadenylation-dependent mRNA degradation, endonucleolytic cleavage-dependent mRNA degradation has not been studied in detail. Previously, we developed truncated RNA-end sequencing (TREseq) in Arabidopsis thaliana and detected G-rich sequence motifs around 5' degradation intermediates. However, it remained to be elucidated whether degradation efficiencies of 5' degradation intermediates in A. thaliana vary among growth conditions and developmental stages. To address this issue, we conducted TREseq of cultured cells under heat stress and at three developmental stages (seedlings, expanding leaves and expanded leaves) and compared 5' degradation intermediates data among the samples. Although some 5' degradation intermediates had almost identical degradation efficiencies, others differed among conditions. We focused on the genes and sites whose degradation efficiencies differed. Changes in degradation efficiencies at the gene and site levels revealed an effect on mRNA accumulation in all comparisons. These changes in degradation efficiencies involved multiple determinants, including mRNA length and translation efficiency. These results suggest that several determinants govern the efficiency of mRNA degradation in plants, helping the organism to adapt to varying conditions by controlling mRNA accumulation.

Different Plant Species Have Common Sequence Features Related to mRNA Degradation Intermediates.

mRNA degradation is an important cellular mechanism involved in the control of gene expression. Several genome-wide profiling methods have been developed for detecting mRNA degradation in plants and animals. However, because many of these techniques use poly (A) mRNA for library preparation, degradation intermediates are often only detected near the 3'-ends of transcripts. Previously, we developed the Truncated RNA End Sequencing (TREseq) method using Arabidopsis thaliana, and demonstrated that this method ameliorates 3'-end bias. In analyses using TREseq, we observed G-rich sequences near the 5'-ends of degradation intermediates. However, this finding remained to be confirmed in other plant species. Hence, in this study, we conducted TREseq analyses in Lactuca sativa (lettuce), Oryza sativa (rice) and Rosa hybrida (rose). These species including A. thaliana were selected to encompass a diverse range in the angiosperm phylogeny. The results revealed similar sequence features near the 5'-ends of degradation intermediates, and involvement of translation process in all four species. In addition, homologous genes have similar efficiencies of mRNA degradation in different plants, suggesting that similar mechanisms of mRNA degradation are conserved across plant species. These strong sequence features were not observed in previous degradome analyses among different species in plants.

Overnight home hemodialysis: eight patients and six years of experience in Sakairumi clinics.

We started our home hemodialysis (HHD) program in July 2005 and have been promoting overnight HHD. As more than 6 years have passed since we started our HHD program, we review our HHD program and 8 overnight HHD patients (5 males and 3 females). Their underlying disease differs in each and none have diabetic nephropathy. Their average age was 49.2 ± 6.0 years (mean ± SD). Average duration of dialysis treatment, HHD, and overnight HHD was 9.4 ± 4.4, 3.5 ± 2.4, and 2.2 ± 1.7 years, respectively. Average treatment time per dialysis session was 6.9 ± 0.8 h/treatment, average treatment days weekly was 4.5 ± 0.8 days/week, and average treatment time weekly was 31.2 ± 7.0 h/week. Laboratory data were good and their blood pressure was well controlled without any antihypertensive drugs excluding a patient who was recently introduced to dialysis with some residual kidney function. Severe problems did not occur in these 6 years except for blood access infection twice, slipping out of a needle during dialysis with small blood loss once, and a drop in blood pressure at the end of dialysis once, which was recovered by her assistant's help. According to our HHD training program, the average training duration for HHD was 106 ± 42 days. The shortest was 60 days and longest 198 days. These differences among training durations might be because of the frequency of training and having a better hand of puncturing. We did not instruct any additional issues and points for overnight HHD, because performing overnight HHD is similar to standard HHD. Some patients moved to overnight HHD slowly starting with once weekly and the others started overnight HHD several days after they had started HHD.