Tunicamycin-induced inhibition of protein secretion into culture medium of Arabidopsis T87 suspension cells through mRNA degradation on the endoplasmic reticulum

The N-glycosylation inhibitor tunicamycin triggers endoplasmic reticulum stress response and inhibits efficient protein secretion in eukaryotes. Using Arabidopsis suspension cells, we showed that the reduced secretion of mannose-binding lectin 1 (MBL1) protein by tunicamycin is accompanied by a significant decrease in MBL1 mRNA, suggesting that mRNA destabilization is the major cause of the inhibition of protein secretion in plants.     

A dynamic reversible RNA N6-methyladenosine modification: current status and perspectives

N⁶-methyladenosine (m⁶A), as the most abundant RNA epigenetic modifications, has been shown to play critical roles in various biological functions. Research about enzymes that can catalyze and remove m⁶A have revealed its comprehensive roles in messenger RNA (mRNA) metabolism and other physiological processes. The “readers” including YTH domain-containing proteins, hnRNPC, hnRNPG, hnRNPA2B1, IGF2BP1, IGF2BP2, and IGF2BP3, which can affect the fates of mRNA in an m⁶A-dependent manner. In this review, we focus on recent advances in the research of the m⁶A modifications, especially about the latest functions of its writers, erasers, readers in RNA metabolism, cancer, and lipid metabolism. In the end, we provide insights into the underlying molecular mechanisms of m⁶A modifications.     

Longevity determined by developmental arrest genes in Caenorhabditis elegans

The antagonistic pleiotropy theory of aging proposes that aging takes place because natural selection favors genes that confer benefit early on life at the cost of deterioration later in life. This theory predicts that genes that impact development would play a key role in shaping adult lifespan. To better understand the link between development and adult lifespan, we examined the genes previously known to be essential for development. From a pool of 57 genes that cause developmental arrest after inhibition using RNA interference, we have identified 24 genes that extend lifespan in Caenorhabditis elegans when inactivated during adulthood. Many of these genes are involved in regulation of mRNA translation and mitochondrial functions. Genetic epistasis experiments indicate that the mechanisms of lifespan extension by inactivating the identified genes may be different from those of the insulin/insulin-like growth factor 1 (IGF-1) and dietary restriction pathways. Inhibition of many of these genes also results in increased stress resistance and decreased fecundity, suggesting that they may mediate the trade-offs between somatic maintenance and reproduction. We have isolated novel lifespan-extension genes, which may help understand the intrinsic link between organism development and adult lifespan.     

Differential regulation of the accumulation of the light-harvesting chlorophyll a/b complex and ribulose bisphosphate carboxylase/oxygenase in greening pea leaves

The photoregulation of chloroplast development in pea leaves has been studied by reference to three polypeptides and their mRNAs. The polypeptides were the large subunit (LSU) and the small subunit (SSU) of ribulose 1,5-bisphosphate carboxylase/oxygenase (RUBISCO), and the light-harvesting chlorophyll a/b protein (LHCP). The polypeptides were assayed by a sensitive radioimmune assay, and the mRNAs were assayed by hybridization to cloned DNA probes. LSU, LSU mRNA, and LHCP mRNA were detectable in etiolated seedlings but LHCP, SSU, and SSU mRNA were at or below the limit of detection. During the first 48 hr of de-etiolation under continuous white light, the mRNAs for LSU, SSU, and LHCP increased in concentration per apical bud by about 40-fold, at least 200-fold, and about 25-fold, respectively, while the total RNA content per apical bud increased only 3.5-fold. In the same period, the LSU, SSU, and LHCP contents per bud increased at least 60-, 100-, and 200-fold, respectively. The LHCP increased steadily in concentration during de-etiolation, whereas the accumulation LSU, SSU, and SSU mRNA showed a 24-hr lag. The accumulation of SSU, SSU mRNA, and LHCP mRNA showed classical red/far-red reversibility, indicating the involvement of phytochrome in the regulatory mechanism. LSU and LSU mRNA were induced equally well by red and far-red light. The LHCP failed to accumulate except under continuous illumination. These results indicate that the accumulation of SSU is controlled largely through the steady-state level of its mRNA, which is in turn almost totally dependent on light as an inducer and on phytochrome as one of the photoreceptors. The accumulation of LSU is largely but not totally determined by the level of its mRNA, which appears to be under strong photoregulation, which has yet to be shown to involve phytochrome. Phytochrome is involved in the regulation of LHCP mRNA levels but substantial levels of the mRNA also occur in the dark. LHCP accumulation is not primarily governed by the levels of LHCP mRNA but by posttranslational stabilization in which chlorophyll synthesis plays a necessary but not sufficient role.     

Sequence of GDF 8 (Myostatin) Gene in Bubalus Bubalis

The sequence of myostatin gene (growth differentiation factor 8 [GDF 8]) in Indian riverine buffalo (Bubalus bubalis) is reported. The genomic DNA as well as mRNA were sequenced. The sequence is conserved across all the livestock species. Five nonsynonymous changes as compared to cattle were found in this study and were also confirmed by mRNA sequence. Two intronic single nucleotide polymorphisms (SNPs) were identified in buffalo.     

cDNA cloning and mRNA expression of calponin and SM22 in rat aorta smooth muscle cells

We cloned and sequenced cDNAs encoding calponin (Calp) and SM22 (smooth muscle-specific 22-kDa protein) from rat aorta (RaA) smooth muscle (Smu) cells. The 1504-bp calp cDNA contains a single open reading frame (ORF) which encodes 297 amino acids (aa) (M_r 33 342). The 1186-bp SM22 cDNA contains a single ORF which encodes 201 aa (M_r 22 601). There were 43% identical aa in a 181-aa overlap between RaA Calp and SM22. Especially for the C-terminal region of SM22 and for the first repeat motif of Calp, 70% identity was observed. Northern blot analysis revealed that the calp and SM22 mRNAs were expressed in RaA Smu, but not in rat cardiac and skeletal muscles. SM22 mRNA was much more abundant than calp mRNA in RaA (3- to 4-fold). The expression levels of the calp and SM22 mRNAs in RaA showed a significant increase for 5 to 15 week old rats (1.5- to 3-fold) with vascular development and blood pressure elevation. No significant differences were observed in the expression of the RaA calp and SM22 mRNAs between normotensive (Wistar Kyoto) and spontaneously hypertensive rats (SHR).