Molecular cloning, sequence and expression analysis of ZmArf2, a maize ADP-ribosylation factor

A maize ADP-ribosylation factor ZmArf2 increases organ and seed size by promoting cell expansion in Arabidopsis

ADP-ribosylation factors (ARFs) are small GTP-binding proteins that regulate a wide variety of cell functions. Previously, we isolated a new ARF, ZmArf2, from maize (Zea mays). Sequence and expression characteristics indicated that ZmArf2 might play a critical role in the early stages of endosperm development. In this study, we investigated ZmArf2 function by analysis of its GTP-binding activity and subcellular localization. We also over-expressed ZmArf2 in Arabidopsis and measured organ and cell size and counted cell numbers. The expression levels of five organ size-associated genes were also determined in 35S::ZmArf2 transgenic and wild-type plants. Results showed that the recombinant ZmArf2 protein purified from Escherichia coli exhibited GTP-binding activity. Subcellular localization revealed that ZmArf2 was localized in the cytoplasm and plasma membrane. ZmArf2 over-expression in Arabidopsis showed that 35S::ZmArf2 transgenic plants were taller and had larger leaves and seeds compared to wild-type plants, which resulted from cell expansions, not an increase in cell numbers. In addition, three cell expansion-related genes, AtEXP3, AtEXP5 and AtEXP10, were upregulated in 35S::ZmArf2 transgenic lines, while the expression levels of AtGIF1 and AtGRF5, were unchanged. Collectively, our studies suggest that ZmArf2 has an active GTP-binding function, and plays a crucial role in growth and development in Arabidopsis through cell expansion mediated by cell expansion genes.

Overexpression of an adenosine diphosphate-ribosylation factor gene from the halophytic grass Spartina alterniflora confers salinity and drought tolerance in transgenic Arabidopsis

Adenosine diphosphate-ribosylation factors (ARFs) are small guanine nucleotide-binding proteins that play an important role in intracellular protein trafficking necessary for undertaking multiple physiological functions in plant growth and developmental processes. However, little is known about the mechanism of ARF functioning at the molecular level, as well as its involvement in abiotic stress tolerance. In this study, we demonstrated the direct involvement of an ARF gene SaARF from a grass halophyte Spartina alterniflora in abiotic stress adaptation for the first time. SaARF, which encodes a protein with predicted molecular mass of 21 kDa, revealed highest identity with ARF of Oryza sativa. The SaARF gene is transcriptionally regulated by salt, drought, cold, and ABA in the leaves and roots of S. alterniflora. Arabidopsis plants overexpressing SaARF showed improved seed germination and survival of seedlings under salinity stress. Similarly, SaARF transgenic Arabidopsis plants were more tolerant to drought stress, compared to wild-type plants, by maintaining chlorophyll synthesis, increasing osmolyte synthesis, and stabilizing membrane integrity. Oxidative damage due to moisture stress in transgenic Arabidopsis was also reduced possibly by activating antioxidant genes, AtSOD1 and AtCAT. Our results suggest that enhanced drought and salinity tolerance conferred by the SaARF gene may be due to its role in mediating multiple abiotic stress tolerance mechanisms.

Cell death-inducing DFFA-like effector c (CIDEC/Fsp27) gene: molecular cloning, sequence characterization, tissue distribution and polymorphisms in Chinese cattles

Cell death-inducing DFFA-like effector c (CIDEC) protein, also known as fat specific protein 27 (Fsp27), is localized to lipid droplets. CIDEC protein is required for unilocular lipid droplet formation and optimal energy storage in addition to controlling lipid metabolism in adipocytes and hepatocytes. Research found that Ad-36 could induce lipid droplets in the cultured skeletal muscle cells and this process may be mediated by promoting CIDEC expression. The content of intermuscular fat is an important index for evaluation of beef quality, so the CIDEC gene appeared to be a candidate gene for regulation of intermuscular fat, however similar research for the bovine CIDEC gene is lacking. This paper examined the tissue expression profile of CIDEC gene in cattle using real-time RT-PCR to suggest that bovine CIDEC is highly expressed in adipose tissue. In addition, the Bovine CIDEC gene was cloned and inserted into the eukaryotic expression vector pET-28a(+), whereupon recombinant bovine CIDEC protein was induced and identified by Western-blot. A phylogenetic analysis showed that the animo acid sequence of bovine CIDEC was closer to mammalian CIDEC than rasorial CIDEC. We found ten single nucleotide polymorphisms sites (SNPs) in bovine CIDEC gene, of which SNP 2, 3, 4, 6 and 9, and SNP 8 and 10 were in complete linkage disequilibrium, respectively. SNP 1, 2 and 10 were used in further haplotype studies. Eight different haplotypes were identified in 973 cattle, of which haplotype 8 predominated with frequencies ranging from 42.90 to 54.30 %. This research provides a basis for future functional studies of CIDEC in cattle.

Identification of differentially expressed genes at two key endosperm development stages using two maize inbreds with large and small grain and integration with detected QTL for grain weight

Maize endosperm accounts for more than 80% of the grain weight. Cell division and grain filling are the two key stages for endosperm development. Previous studies showed that gene expression during differential stages in endosperm development is greatly different. However, information on systematic identification and characterization of the differentially expressed genes between the two stages are limited. In this study, suppression subtractive hybridization (SSH) was used to generate four subtracted cDNA libraries for the two stages using two maize inbreds with large and small grain. Totally, 4,784 differentially expressed sequence tags (ESTs) were sequenced and 902 were non-redundant, which consisted of 344 unique ESTs. Among them 192 had high sequence similarity to the GenBank entries and represent diverse of functional categories, such as metabolism, cell growth/division, transcription, signal transduction, protein destination/storage, protein synthesis and others. The expression patterns of 75.7% SSH-derived cDNAs were confirmed by reverse Northern blot and semi-quantitative reverse transcription polymerase chain reaction, and exhibited the similar results (75.0%). Genes differentially expressed between two key stages for the two inbreds were involved in diverse physiological process pathway, which might be responsible for the formation of grain weight. 43.8% (70 of the 160 unique ESTs) of the identified ESTs were assigned to 39 chromosome bins distributed over all ten maize chromosomes. Eleven ESTs were found to co-localize with previous detected QTLs for grain weight, which might be considered as the candidate genes of grain weight for further study.