A characteristic mechanism of gene expression regulation during seed germination is the selective translation of mRNAs. Previous findings indicate that the two cap-binding complexes eIF4F (with eIF4E and eIF4G subunits) and eIF(iso)4F [with eIF(iso)4E and eIF(iso)4G subunits] are differentially expressed during maize seed germination. In addition, several studies in vitro have suggested that these factors may participate in selective mRNA translation. The translational activities of eIF4E and eIF(iso)4E were tested in vitro using transcripts from two different sets: dry (0 h) and 24-h-imbibed maize embryonic axes. In vitro translation of these mRNA pools in the presence of the recombinant eIF4E or eIF(iso)4E, and the native cap-binding complexes from dry- or 24-h-imbibed axes, produced different profiles of proteins which were visualized by two-dimensional protein gels and autoradiography. The data indicated that eIF(iso)4E was particularly required for translation of the stored mRNAs from dry seeds, and that eIF4E was unable to fully replace the eIF(iso)4E activity. In addition, the dry seed mRNA pool was translated by the cap-binding complex isolated from dry seeds better than by the complex isolated from 24-h-imbibed seeds, whereas the translational efficiency of the mRNA pool from 24-h-imbibed seeds was similar between the cap-binding complexes from these two stages. Interestingly, eIF(iso)4E was more abundant than eIF4E in dry seeds, while both cap-binding proteins were present at similar levels in 24-h-imbibed seeds. These results suggest that the ratio of eIF(iso)4E to eIF4E in the corresponding eIF4F complex is critical for the mechanisms of translational control during maize germination.

Many Cactaceae species exhibit determinate growth of the primary root as a consequence of root apical meristem (RAM) exhaustion. The genetic regulation of this growth pattern is unknown. Here, we de novo assembled and annotated the root apex transcriptome of the Pachycereus pringlei primary root at three developmental stages, with active or exhausted RAM. The assembled transcriptome is robust and comprehensive, and was used to infer a transcriptional regulatory network of the primary root apex. Putative orthologues of Arabidopsis regulators of RAM maintenance, as well as putative lineage-specific transcripts were identified. The transcriptome revealed putative orthologues of most proteins involved in housekeeping processes, hormone signalling, and metabolic pathways. Our results suggest that specific transcriptional programs operate in the root apex at specific developmental time points. Moreover, the transcriptional state of the P. pringlei root apex as the RAM becomes exhausted is comparable to the transcriptional state of cells from the meristematic, elongation, and differentiation zones of Arabidopsis roots along the root axis. We suggest that the transcriptional program underlying the drought stress response is induced during Cactaceae root development, and that lineage-specific transcripts could contribute to RAM exhaustion in Cactaceae.

Maize heat shock protein HSP101 accumulates during embryo maturation and desiccation and persists at high levels during the first 24 h following kernel imbibition in the absence of heat stress. This protein has a known function in disaggregation of high molecular weight complexes and has been proposed to be a translational regulator of specific mRNAs. Here, a global proteomic approach was used to identify changes in the maize proteome due to the absence of HSP101 in embryos from mature-dry or 24 h-imbibed kernels. A total of 26 protein spots from the mature dry embryo exhibited statistically significant expression changes in the L10 inbred hsp101 mutant (hsp101-m5::Mu1/hsp101-m5::Mu1) line as compared to the corresponding wild type (Hsp101/Hsp101). Additional six spots reproducibly showed qualitative changes between the mutant and wild-type mature and germinating embryos. Several chaperones, translation-related proteins, actin, and enzymes participating in cytokinin metabolism were identified in these spots by tandem mass-spectrometry (MS). The proteomic changes partially explain the altered root growth and architecture observed in young hsp101 mutant seedlings. In addition, specific protein de novo synthesis was altered in the 24 h-imbibed mutant embryos indicating that maize HSP101 functions as both chaperone and translational regulator during germination. Supporting this, HSP101 was found as part of Cap-binding and translation initiation complexes during early kernel imbibition. Overall, these findings expose the relevance of maize HSP101 for protein synthesis and balance mechanisms during germination.

This work describes the identification of components in the Cap-binding complexes in non-germinated and 24-h-imbibed seeds using mass spectrometry. This approach revealed new components particularly present in the non-germinated seed. Among these, two heat shock proteins, HSP101 and HSP70, were detected as well as several proteins involved in carbohydrate metabolism. Between the new components of maize Cap-binding complexes, several proteins contain a motif that identifies them as potential direct interactors with eIF4E or eIF(iso)4E.Together with the major abundance of eIF(iso)4E at this developmental stage, our findings indicate clear differences between the translation initiation complexes that are available for protein synthesis right upon water imibition and those that are present once germination has been completed.

The incidence of human cervix adenocarcinoma (CC) caused by papillomavirus genome integration into the host chromosome is the third most common cancer among women. Bacterial cyclodipeptides (CDPs) exert cytotoxic effects in human cervical cancer HeLa cells, primarily by blocking the PI3K/Akt/mTOR pathway, but downstream responses comprising gene expression remain unstudied. Seeking to understand the cytotoxic and anti-proliferative effects of CDPs in HeLa cells, a global RNA-Seq analysis was performed. This strategy permitted the identification of 151 differentially expressed genes (DEGs), which were either up- or down-regulated in response to CDPs exposure. Database analysis, including Gene Ontology (COG), and the Kyoto Encyclopedia of Genes and Genomes (KEGG), revealed differential gene expression on cancer transduction signals, and metabolic pathways, for which, expression profiles were modified by the CDPs exposure. Bioinformatics confirmed the impact of CDPs in the differential expression of genes from signal transduction pathways such as PI3K-Akt, mTOR, FoxO, Wnt, MAPK, P53, TGF-β, Notch, apoptosis, EMT, and CSC. Additionally, the CDPs exposure modified the expression of cancer-related transcription factors involved in the regulation of processes such as epigenetics, DNA splicing, and damage response. Interestingly, transcriptomic analysis revealed the participation of genes of the mevalonate and cholesterol biosynthesis pathways; in agreement with this observation, total cholesterol diminished, confirming the blockage of the cholesterol synthesis by the exposure of HeLa cells to CDPs. Interestingly, the expression of some genes of the mevalonate and cholesterol synthesis such as HMGS1, HMGCR, IDI1, SQLE, MSMO1, SREBF1, and SOAT1 was up-regulated by CDPs exposure. Accordingly, metabolites of the mevalonate pathway were accumulated in cultures treated with CDPs. This finding further suggests that the metabolism of cholesterol is crucial for the occurrence of CC, and the blockade of the sterol synthesis as an anti-proliferative mechanism of the bacterial CDPs, represents a reasonable chemotherapeutic drug target to explore. Our transcriptomic study supports the anti-neoplastic effects of bacterial CDPs in HeLa cells shown previously, providing new insights into the transduction signals, transcription factors and metabolic pathways, such as mevalonate and cholesterol that are impacted by the CDPs and highlights its potential as anti-neoplastic drugs.