Aluminum (Al) toxicity is the major limiting factor of crop production on acid soils, but some plant species have evolved ways of detoxifying Al. Here, we report a C2H2-type zinc finger transcription factor ART1 (for Al resistance transcription factor 1), which specifically regulates the expression of genes related to Al tolerance in rice (Oryza sativa). ART1 is constitutively expressed in the root, and the expression level is not affected by Al treatment. ART1 is localized in the nucleus of all root cells. A yeast one-hybrid assay showed that ART1 has a transcriptional activation potential and interacts with the promoter region of STAR1, an important factor in rice Al tolerance. Microarray analysis revealed 31 downstream transcripts regulated by ART1, including STAR1 and 2 and a couple of homologs of Al tolerance genes in other plants. Some of these genes were implicated in both internal and external detoxification of Al at different cellular levels. Our findings shed light on comprehensively understanding how plants detoxify aluminum to survive in an acidic environment.

Phytotoxicity of aluminum is characterized by a rapid inhibition of root elongation at micromolar concentrations, however, the mechanisms primarily responsible for this response are not well understood. We investigated the effect of Al on the viscosity and elasticity parameters of root cell wall by a creep-extension analysis in two cultivars of wheat (Triticum aestivum L.) differing in Al resistance. The root elongation and both viscous and elastic extensibility of cell wall of the root apices were hardly affected by the exposure to 10 microM Al in an Al-resistant cultivar, Atlas 66. However, similar exposure rapidly inhibited root elongation in an Al-sensitive cultivar, Scout 66 and this was associated with a time-dependent accumulation of Al in the root tissues with more than 77% residing in the cell wall. Al caused a significant decrease in both the viscous and elastic extensibility of cell wall of the root apices of Scout 66. The "break load" of the root apex of Scout 66 was also decreased by Al. However, neither the viscosity nor elasticity of the cell wall was affected by in vitro Al treatment. Furthermore, pre-treatment of seedlings with Al in conditions where root elongation was slow (i.e. low temperature) did not affect the subsequent elongation of roots in a 0 Al treatment at room temperature. These results suggest that the Al-dependent changes in the cell wall viscosity and elasticity are involved in the inhibition of root growth. Furthermore, for Al to reduce cell wall extensibility it must interact with the cell walls of actively elongating cells.

Rice (Oryza sativa L. cv Oochikara) is a typical silicon-accumulating plant, but the mechanism responsible for the high silicon uptake by the roots is poorly understood. We characterized the silicon uptake system in rice roots by using a low-silicon rice mutant (lsi1) and wild-type rice. A kinetic study showed that the concentration of silicon in the root symplastic solution increased with increasing silicon concentrations in the external solution but saturated at a higher concentration in both lines. There were no differences in the silicon concentration of the symplastic solution between the wild-type rice and the mutant. The form of soluble silicon in the root, xylem, and leaf identified by 29 Si-NMR was also the same in the two lines. However, the concentration of silicon in the xylem sap was much higher in the wild type than in the mutant. These results indicate that at least two transporters are involved in silicon transport from the external solution to the xylem and that the low-silicon rice mutant is defective in loading silicon into xylem rather than silicon uptake from external solution to cortical cells. To map the responsible gene, we performed a bulked segregant analysis by using both microsatellite and expressed sequence tag-based PCR markers. As a result, the gene was mapped to chromosome 2, flanked by microsatellite marker RM5303 and expressed sequence tag-based PCR marker E60168.Rice (Oryza sativa L. cv Oochikara) requires high silicon for healthy growth and stable and high productivity (Savant et al., 1997;Ma and Takahashi, 2002). Silicon at up to 10% of dry weight is accumulated in the shoot, and more than 90% of silicon is present in the form of silica gel (Ma and Takahashi, 2002). Silica gel is deposited on the cell wall of epidermal cells of leaves, stems, and hulls, forming a silica-cuticle double layer and a silica-cellulose double layer (Yoshida, 1965;Raven, 2003). Silicon is also deposited on the bulliform cells, dumbbell cells, and long and short cells on the surface of leaves and hulls. The deposition of silicon enhances the strength and rigidity of cell walls and thus increases the resistance of rice to diseases, pests, and lodging, improving light-receiving plant form in a community and decreasing transpiration (Epstein, 1994(Epstein, , 1999Ma and Takahashi, 2002;Ma, 2003). Thus, silicon plays an important role in enhancing the resistance of rice to multiple stresses, including biotic and abiotic stresses (Ma, 2004). Silicate fertilizer has been applied to paddy soils to increase rice productivity.High accumulation of silicon in rice has been attributed to the ability of the roots to take up silicon (Takahashi et al., 1990;Richmond and Sussman, 2003). Recently, a rice mutant that has a low silicon concentration in the shoots was isolated from sodium azidetreated M 2 seeds of rice . This mutant (low silicon rice 1, lsi1, formerly GR1) had a plant type similar to the wild type except that the leaf blade of lsi1 remained droopy when silicon was supplied. The silicon concentration of t...

Aluminium (Al) toxicity is an important limitation to barley (Hordeum vulgare L.) on acid soil. Al-resistant cultivars of barley detoxify Al externally by secreting citrate from the roots. To link the genetics and physiology of Al resistance in barley, genes controlling Al resistance and Al-activated secretion of citrate were mapped. An analysis of Al-induced root growth inhibition from 100 F2 seedlings derived from an Al-resistant cultivar (Murasakimochi) and an Al-sensitive cultivar (Morex) showed that a gene associated with Al resistance is localized on chromosome 4H, tightly linked to microsatellite marker Bmag353. Quantitative trait locus (QTL) analysis from 59 F4 seedlings derived from an F3 plant heterozygous at the region of Al resistance on chromosome 4H showed that a gene responsible for the Al-activated secretion of citrate was also tightly linked to microsatellite marker Bmag353. This QTL explained more than 50% of the phenotypic variation in citrate secretion in this population. These results indicate that the gene controlling Al resistance on barley chromosome 4H is identical to that for Al-activated secretion of citrate and that the secretion of citrate is one of the mechanisms of Al resistance in barley. The identification of the microsatellite marker associated with both Al resistance and citrate secretion provides a valuable tool for marker-assisted selection of Al-resistant lines.

Rice (Oryza sativa L.) is a highly Al-resistant species among small grain crops, but the mechanism responsible for the high Al resistance has not been elucidated. In this study, rice mutants sensitive to Al were isolated from M(3) lines derived from an Al-resistant cultivar, Koshihikari, irradiated with gamma-rays. Relative root elongation was used as a parameter for evaluating Al resistance. After initial screening plus two rounds of confirmatory testing, a mutant (als1) was isolated from a total of 560 lines. This mutant showed a phenotype similar to the wild-type plant in the absence of Al. However, in the presence of 10 microM Al, root elongation was inhibited 70% in the mutant, but only 8% in the wild-type plant. The mutant also showed poorer root growth in acid soil. The Al content of root apices (0-1 cm) was much lower in the wild-type plant. The sensitivity to other metals including Cd and La did not differ between the mutant and the wild-type plants. A small amount of citrate was secreted from the roots of the mutant in response to Al stress, but there was no difference from that secreted by the wild-type plant. Genetic analysis of F(2) populations between als1 and wild-type plants showed that the Al-resistant seedlings and Al-sensitive seedlings segregated at a 3 : 1 ratio, indicating that the high sensitivity to Al in als1 is controlled by a single recessive gene. The gene was mapped to the long arm of chromosome 6, flanked by InDel markers MaOs0619 and MaOs0615.

The effects of incretins on ovarian steroidogenesis have not been clarified. In this study, we investigated the effects of incretins, including GIP and GLP-1, on ovarian steroidogenesis using rat primary granulosa cells. Treatment with incretins significantly suppressed progesterone synthesis in the presence of FSH, and the effect of GIP was more potent than that of GLP-1. In contrast, incretins had no significant effect on estrogen synthesis by rat granulosa cells. In accordance with the effects of incretins on steroidogenesis, GIP and GLP-1 suppressed the expression of progesterogenic factors and enzymes, including StAR, P450scc, 3βHSD, but not P450arom, and cellular cAMP synthesis induced by FSH. In addition, incretins moderately increased FSHR mRNA expression in granulosa cells. Of note, treatment with GIP, but not treatment with GLP-1, augmented Smad1/5/8 phosphorylation and transcription of the BMP target gene Id-1 induced by BMP-6 stimulation, suggesting that GIP upregulates BMP receptor signaling that can inhibit FSH-induced progesterone synthesis in rat granulosa cells. On the other hand, BMP-6 treatment suppressed the expression of GIP receptor but not that of GLP-1 receptor. Expression of the BMP type-I receptor ALK-3 was upregulated by treatment with GIP and GLP-1 and that of ALK-6 was also increased by GIP, while inhibitory Smad6 expression was impaired by GIP and GLP-1 in rat granulosa cells. Collectively, the results indicate that incretins, particularly GIP, impair FSH-induced progesterone production, at least in part, by upregulating BMP signaling in rat granulosa cells. The modulatory effects of incretins on endogenous BMP activity may be applicable to treatment of dysregulated steroidogenesis such as polycystic ovary syndrome.

HighlightsMassive bleeding from the thyroid without direct neck trauma rarely causes airway compromise.Physicians should regard possible thyroid gland rupture in patients with swelling of the neck or acute respiratory failure after direct/indirect trauma to the neck.Airway management is the most important consideration in such patients with thyroid injury.

A functional link between clock gene expression and ovarian steroidogenesis was studied using human granulosa KGN cells. Similarities between changes in the mRNA and protein expression levels of Bmal1 and Clock and those of Per2 and Cry1 were found in KGN cells after treatment with forskolin. Among the interrelationships between the expression levels of clock and steroidogenic factors, Clock mRNA had a strongly positive correlation with P450arom and a negative correlation with 3βHSD. Knockdown of Clock gene by siRNA resulted in a significant reduction of estradiol production by inhibiting P450arom expression, while it induced a significant increase of progesterone production by upregulating 3βHSD in KGN cells treated with forskolin. Moreover, BMP-7 had an enhancing effect on the expression of Clock mRNA and protein in KGN cells. Thus, the expression levels of Clock, being upregulated by forskolin and BMP-7, were functionally linked to estradiol production and progesterone suppression by human granulosa cells. IN MAMMALS, the expression of clock-related geneshas been demonstrated in tissues composing the axis of the hypothalamic-pituitary-gonadal system [1-3]. Functional roles of the hypothalamus in the biological timings and rhythms for control of the reproductive axis have been gradually recognized. However, the significance of clock-related genes expressed in ovarian follicles and granulosa cells has remained unclear.Results of recent studies have shown that clock genes are expressed in the ovary, and accumulated findings have demonstrated a significant interrelationship be-