Dietary E. coli promotes age-dependent chemotaxis decline in C. elegans.

An animal's ability to sense odors declines during aging, and its olfactory drive is tuned by internal states such as satiety. However, whether internal states modulate an age-dependent decline in odor sensation is unknown. To address this issue, we utilized the nematode Caenorhabditis elegans and compared their chemotaxis abilities toward attractive odorants when aged under different dietary conditions. Feeding with the standard laboratory diet, Escherichia coli attenuated the chemotaxis ability toward diacetyl, isoamyl alcohol, and benzaldehyde when aged. On the other hand, feeding with either the lactic acid bacteria Lactobacillus reuteri or food deprivation selectively maintained the chemotaxis ability toward diacetyl. Our results suggest that ingestion of E. coli causes age-dependent chemotaxis decline. The changes in the chemotaxis behavior are attributed to the different expressions of diacetyl receptor odr-10, and the chemotaxis behavior of aged animals under food deprivation is shown to be dependent on daf-16. Our study demonstrates the molecular mechanism of how diet shapes the trajectory of age-dependent decline in chemosensory behaviors.

[Functional analysis of vernalization-related gene VER17 in flower development using antisense RNA strategy in winter wheat].

To understand the function of vernalization-related gene VER17 in winter wheat (Triticum aestivum L. cv. Jingdong No.1), an antisense RNA strategy was used. The antisense VER17 with a vector pBI121 was constructed and transformed into winter wheat by using the pollen-tube-pathway method. Fourteen independent transgenic plants transformed with antisense VER17 and five control transformants transformed with pBI121 blank vector were obtained and confirmed by GUS histochemical assay and PCR-Southern blot analysis. Phenotypes of T(0) and T(1) transgenic plants showed that the plants of the antisense VER17 transgenic lines degenerated top or basal spikelets and had delayed flowering time, which suggested that the VER17 gene functions in accelerating flowering and the development of the top or basal spikelets and the stamen which were impacted by vernalization treatment.

Functional analysis of the ver gene using antisense transgenic wheat.

The function of ver203, a gene related to vernalization in winter wheat, was investigated by expression of a complementary DNA as an antisense RNA in transgenic plants. A verc203:gus fusion-expression plasmid was constructed in pBI221, which contains a CaMV (cauliflower mosaic virus) 35S-promoter, a gus gene and a nos terminator. The construct was then introduced into the plant by the pollen-tube pathway. The results showed that heading was strongly inhibited in 6 of 326 vernalized antisense transgenic winter wheat plants, until both the vernalized control winter wheat and sense transgenic plants ripened. The hybridization analysis of DNA, amplification of the insert DNA sequences with PCR, northern blot analysis with double- and single-stranded probes, and detection of GUS activity by X-gluc assay gave strong positive results. This suggests that the VER203 protein plays an important role in controlling heading and flower development in winter wheat.

Cloning and characteristics of an allene oxide synthase gene (TaAOS) of winter wheat.

Allene oxide synthase (AOS) is the first enzyme in the lipoxygenase pathway which leads to the formation of jasmonic acid (JA). A full length cDNA of TaAOS was cloned in winter wheat (Triticum aestivum L. cv. Jinghua No.3) seedlings. The open reading frame encompassed 1410 bp encoding a polypeptide of 470 amino acids with calculated molecular mass of 51.9 kD. Southern blot analysis suggested there are three copies of the gene in wheat genome. The TaAOS mRNA could be strongly induced by exogenous JA, and the highest level JA was observed after a 10 h induction. In situ RNA hybridization of seedling indicated preferential gene expression in young leaves, especially in the parenchyma cells around the vascular bundles, and the hybridization also showed that exogenous La(3+) could not suppress the expression of TaAOS induced by JA.

Overexpression of OsRAA1 causes pleiotropic phenotypes in transgenic rice plants, including altered leaf, flower, and root development and root response to gravity.

There are very few root genes that have been described in rice as a monocotyledonous model plant so far. Here, the OsRAA1 (Oryza sativa Root Architecture Associated 1) gene has been characterized molecularly. OsRAA1 encodes a 12.0-kD protein that has 58% homology to the AtFPF1 (Flowering Promoting Factor 1) in Arabidopsis, which has not been reported as modulating root development yet. Data of in situ hybridization and OsRAA1::GUS transgenic plant showed that OsRAA1 expressed specifically in the apical meristem, the elongation zone of root tip, steles of the branch zone, and the young lateral root. Constitutive expression of OsRAA1 under the control of maize (Zea mays) ubiquitin promoter resulted in phenotypes of reduced growth of primary root, increased number of adventitious roots and helix primary root, and delayed gravitropic response of roots in seedlings of rice (Oryza sativa), which are similar to the phenotypes of the wild-type plant treated with auxin. With overexpression of OsRAA1, initiation and growth of adventitious root were more sensitive to treatment of auxin than those of the control plants, while their responses to 9-hydroxyfluorene-9-carboxylic acid in both transgenic line and wild type showed similar results. OsRAA1 constitutive expression also caused longer leaves and sterile florets at the last stage of plant development. Analysis of northern blot and GUS activity staining of OsRAA1::GUS transgenic plants demonstrated that the OsRAA1 expression was induced by auxin. At the same time, overexpression of OsRAA1 also caused endogenous indole-3-acetic acid to increase. These data suggested that OsRAA1 as a new gene functions in the development of rice root systems, which are mediated by auxin. A positive feedback regulation mechanism of OsRAA1 to indole-3-acetic acid metabolism may be involved in rice root development in nature.

Vernalization-induced flowering in wheat is mediated by a lectin-like gene VER2.

A vernalization-related gene VER2 was isolated from winter wheat ( Triticum aestivum L.) using a differential screening approach. The deduced VER2 is a lectin-like protein of 300 amino acids, which contains the presence of a jacalin-like GWG domain. RNA in situ hybridization results demonstrated that VER2 gene expression is restricted to the marginal meristems of immature leaves in vernalized wheat seedlings. No hybridization signal was detected in the epidermal tissue and vascular bundles. However, "devernalization" resulted in the silencing of VER2 gene activity. The gene expression pattern of VER2 induced by jasmonate was similar to that induced by vernalization. Antisense inhibition of VER2 in transgenic wheat showed that heading and maturation time were delayed up to 6 weeks compared with non-transformed wheat and the pBI121empty-vector-transformed wheat. Tissue degeneration at the top of the spike was also noticed in the antisense inhibited transgenic wheat. These results suggest that VER2 plays an important role in vernalization signaling and spike development in winter wheat.