RESUMEN
Canola (Brassica napus) is a widely cultivated species and provides important resources of edible vegetable oil, biodiesel production and animal feed. Seed development in Arabidopsis and canola shares a similar path: an early proliferation of endosperm to form a large seed cavity, followed by a second phase in which the embryo grows to replace the endosperm. In Arabidopsis, the seed reaches almost its final volume before the enlargement of the embryo. SHORT HYPOCOTYL UNDER BLUE1 (SHB1) is a key regulatory gene of seed development with a broad expression beyond endosperm development. By contrast, its two target genes, MINISEED3 (MINI3) and HAIKU2 (IKU2), are narrowly expressed in early developing endosperm and early embryo. We overexpressed SHB1 in canola to explore the possibility of altering seed development. As an alternative strategy, we expressed the canola IKU2 ortholog in Arabidopsis endosperm under the control of a stronger MINI3 promoter. SHB1 targeted canola orthologs of Arabidopsis MINI3 and IKU2 and caused a significantly increased seed mass. Overaccumulation of IKU2 in the early stage of Arabidopsis seed development also significantly increased the final seed mass. Our studies provide a strong case for increasing the final seed mass by manipulating endosperm proliferation at a rather early developmental stage in crops.
Asunto(s)
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Brassica napus/genética , Proteínas Quinasas/genética , Semillas/crecimiento & desarrollo , Arabidopsis/crecimiento & desarrollo , Proteínas de Arabidopsis/metabolismo , Brassica napus/crecimiento & desarrollo , Regulación de la Expresión Génica de las Plantas , Mutación , Fenotipo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente/genética , Regiones Promotoras Genéticas , Proteínas Quinasas/metabolismo , Semillas/química , Semillas/genética , Factores de Transcripción/genéticaRESUMEN
Aluminium (Al) toxicity and phosphorus (P) deficiency are considered to be the main constraints for crop production in acid soils, which are widely distributed in tropical and subtropical regions. Conventionally, P addition is regarded as capable of alleviating Al toxicity in plants. However, this field is still rife with unsubstantiated theories, especially for different plant species growing on acid soils. In this review, the responses of plants to different methods of Al-P treatments are briefly summarized, and possible reasons are proposed by considering recent results from our laboratory. It is shown that: (1) long-term Al-P alternate treatment is advantageous for studying Al-P interactions in plants; (2) under the long-term Al-P alternate treatment, the roles of P in Al phytotoxicity might be associated with the Al resistance capability and P use efficiency of the plant, and a P/Al molar ratio exceeding 5 in roots may be the threshold of P alleviating Al toxicity based on the calculation of the tested plants; (3) in acid soils, P application may be effective only after Al stress is overcome for Al-sensitive species. Thus it is concluded that P application does not always alleviate Al toxicity under long-term Al-P alternate treatment.
Asunto(s)
Aluminio/toxicidad , Productos Agrícolas/metabolismo , Fósforo/metabolismo , Suelo/química , Ácidos , Aluminio/metabolismo , Productos Agrícolas/crecimiento & desarrollo , Humanos , Concentración de Iones de HidrógenoRESUMEN
This study was conducted with amaranth as a representative leafy vegetable to elucidate the effects of application of different fertilizers such as inorganic nitrogen and organic fertilizers, which were widely used in agricultural production, on the extractable concentrations of polycyclic aromatic hydrocarbons (PAHs) in aged contaminated soil under a greenhouse incubation experiment. The results show that the extractable concentrations of phenanthrene (Phe), fluoranthene (Flt) and benzo (b) fluoranthene (BbF) decrease significantly in organic fertilizer treatments than those in inorganic nitrogen fertilizer treatments (p < 0.05). In the same sampling time and treatment, the ratios of extractable concentrations to primary concentrations in aged contaminated soil of three PAHs increase in an order, BbF < Flt < Phe (p < 0.05), showing that the adsorption of PAHs among soil components varies clearly with their physicochemical properties. The extractable concentrations of three PAHs are significantly higher in unvegetated soil than those in rhizosphere soil (p < 0.05).
Asunto(s)
Amaranthus/crecimiento & desarrollo , Fertilizantes , Hidrocarburos Policíclicos Aromáticos/análisis , Contaminantes del Suelo/análisis , Fluorenos/análisis , Fenantrenos/análisis , Hidrocarburos Policíclicos Aromáticos/química , Contaminantes del Suelo/químicaRESUMEN
BACKGROUND AND AIMS: Aluminium (Al) toxicity and phosphorus (P) deficiency often co-exist in acidic soils and limit crop production worldwide. Lespedeza bicolor is a leguminous forage species that grows very well in infertile, acidic soils. The objective of this study was to investigate the effects of Al and P interactions on growth of Lespedeza and the distributions of Al and P in two different Al-resistant species, and to explore whether P can ameliorate the toxic effect of Al in the two species. METHODS: Two species, Lespedeza bicolor and L. cuneata, were grown for 30 d with alternate Al and P treatments in a hydroponics system. Harvested roots were examined using a root-system scanner, and the contents of Al, P and other nutrient elements in the plants were determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Haematoxylin staining was used to observe the distribution of Al in the roots of seedlings. After pre-culture with or without P application, organic acids in the exudates of roots exposed to Al were held in an anion-exchange resin, eluted with 2 m HCl and then analysed using high-performance liquid chromatography (HPLC). KEY RESULTS: Lespedeza bicolor exhibited a stronger Al resistance than did L. cuneata; Al exclusion mechanisms may mainly be responsible for resistance. P application alleviated the toxic effect of Al on root growth in L. bicolor, while no obvious effects were observed in L. cuneata. Much less Al was accumulated in roots of L. bicolor than in L. cuneata after P application, and the P contents in both roots and shoots increased much more for L. bicolor than for L. cuneata. Lespedeza bicolor showed a higher P/Al ratio in roots and shoots than did L. cuneata. P application decreased the Al accumulation in root tips of L. bicolor but not in L. cuneata. The amount of Al-induced organic acid (citrate and malate) exudation from roots pre-cultured with P was much less than from roots without P application; no malate and citrate exudation was detected in L. cuneata. CONCLUSIONS: P enhanced Al resistance in the Al-resistant L. bicolor species but not in the Al-sensitive L. cuneata under relatively high Al stress, although P in L. cuneata might also possess an alleviative potential. Enhancement of Al resistance by P in the resistant species might be associated with its more efficient P accumulation and translocation to shoots and greater Al exclusion from root tips after P application, but not with an increased exudation of organic acids from roots.