Regulation by distinct MYB transcription factors defines the roles of OsCYP86A9 in anther development and root suberin deposition.

Cytochrome P450 proteins (CYPs) play critical roles in plant development and adaptation to fluctuating environments. Previous reports have shown that CYP86A proteins are involved in the biosynthesis of suberin and cutin in Arabidopsis. However, the functions of these proteins in rice remain obscure. In this study, a rice mutant with incomplete male sterility was identified. Cytological analyses revealed that this mutant was defective in anther development. Cloning of the mutant gene indicated that the responsible mutation was on OsCYP86A9. OsMYB80 is a core transcription factor in the regulation of rice anther development. The expression of OsCYP86A9 was abolished in the anther of osmyb80 mutant. In vivo and in vitro experiments showed that OsMYB80 binds to the MYB-binding motifs in OsCYP86A9 promoter region and regulates its expression. Furthermore, the oscyp86a9 mutant exhibited an impaired suberin deposition in the root, and was more susceptible to drought stress. Interestingly, genetic and biochemical analyses revealed that OsCYP86A9 expression was regulated in the root by certain MYB transcription factors other than OsMYB80. Moreover, mutations in the MYB genes that regulate OsCYP86A9 expression in the root did not impair the male fertility of the plant. Taken together, these findings revealed the critical roles of OsCYP86A9 in plant development and proposed that OsCYP86A9 functions in anther development and root suberin formation via two distinct tissue-specific regulatory pathways.

Magnesium may be a key nutrient mechanism related to Fusarium wilt resistance: a new banana cultivar (Zhongjiao No. 9).

Zhongjiao No. 9 (Musa spp.), a new Fusarium wilt-resistant banana cultivar, has shown considerable promise in the field. However, the growth, nutrient budgets, and key nutrient mechanisms related to Fusarium wilt resistance have not been explicitly examined. Here, the plant growth, yield, fruit quality, and nutrient budgets of Zhongjiao No. 9 were investigated. The results showed that Zhongjiao No. 9 has a large biomass with a high yield (54.65 t ha-1). The concentrations of N, P, K, Ca, Mg, Mn, B, and Mo were mainly high in the leaves and bunches of mother plants as well as in the leaves and pseudostems of daughter plants, while Cu and Fe were enriched in the roots of both mother plants and daughter plants. Linear discriminant analysis revealed that K, Ca, and Fe were important for plant growth in both the mother plants and daughter plants; S, Zn, and Mn were important for the mother plants, and N, P, and B for were important for the daughter plants. The nutrient uptake ratio of N:P:K:Ca:Mg:S was 1:0.13:3.86:0.68:0.40:0.07. Compared with local cultivars, there was a higher Mg concentration in pseudostems and a higher Mg uptake ratio were observed in Zhongjiao No. 9. Together, our results provide insight into the importance of Mg accumulation in relation to Fusarium wilt resistance, and we provide information on nutrient demands and fertilization application.

Effect of roxarsone metabolites in chicken manure on soil biological property.

Roxarsone (ROX), an organoarsenic feed additive, occurs as itself and its metabolites including As(V), As(III), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in animal manure. Animal manure improves soil biological property, whereas As compounds impact microorganisms. The integral influence of animal manure bearing ROX metabolites on soil biological quality is not clear yet. Herein, the effect of four chicken manures excreted by chickens fed with four diets containing 0, 40, 80 and 120 mg ROX kg-1, on soil biological attributes. ROX addition in chicken diets increased total As and ROX metabolites in manures, but decreased manure total N, ammonium and nitrate. The elevated ROX metabolites in manures increased soil total As, As species and total N, and increased first and then decreased soil nitrate and nitrite, but did not affect soil ammonium in manure-applied soils. The promoting role of both soil As(III) and ammonium on soil microbial biomass carbon and nitrogen, respiration and saccharase activity, were exceeded or balanced by the inhibiting effect of soil nitrate. The suppression of soil catalase activity by soil As(V) was surpassed by the enhancement caused by soil nitrate and nitrite. Soil urease, acid phosphatase and polyphenol oxidase activities were not suitable bioindicators in the four manure-amended soils. Soil DMA did not affect soil biological properties, and MMA was not detectable in all manure-amended soils. The above highlights the complexity of joint influence of soil As and N on biological attributes. Totally, when ROX is used at allowable dose in chicken diet, soil biological quality would be suppressed in manure-amended soil.

Soil calcium significantly promotes uptake of inorganic arsenic by garland chrysanthemum (ChrysanthemumL coronarium) fertilized with chicken manure bearing roxarsone and its metabolites.

Roxarsone (ROX), a widely used feed organoarsenic additive, occurs as itself and its metabolites in animal manure that is commonly land used as fertilizer. Soil property impacts arsenic (As) speciation and bioavailability. Fourteen soils across China were used to conduct culture experiments to investigate As uptake by garland chrysanthemum (ChrysanthemumL coronarium), with the soils fertilized with chicken manure bearing ROX and its metabolites. The results show As(III) was the sole As form in garland chrysanthemum shoots, and As(III) and As(V) occurred in roots. Only inorganic As was detected in all soils when the plants were harvested. Stepwise regression analysis shows soil-exchangeable Ca predominated shoot As(III) concentration (shoot As(III) = 1.60030 soil Ca, R 2 = 0.8832***). Therefore, ROX is transferred into the human food chain finally as inorganic As in plants. Application of animal manure bearing ROX and its metabolites is not recommended in Ca-rich soils to avoid excess inorganic As dietary exposure.

Delivery of roxarsone via chicken diet→chicken→chicken manure→soil→rice plant.

Roxarsone (ROX), a widely used feed additive, occurs as itself and its metabolites in animal manure. Rice is prone to accumulate As than other staple food. Four diets with 0, 40, 80 and 120mgROXkg(-1) were fed in chickens, and four chicken manures (CMs) were collected to fertilize rice plants in a soil culture experiment. Linear regression analysis shows that the slopes of As species including 4-hydroxy-phenylarsonic acid, As(V), As(III), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in CM versus dietary ROX were 0.033, 0.314, 0.033, 0.054 and 0.138, respectively. Both As(III) and DMA were determined in all rice grains, and As(III), As(V), MMA and DMA in rice hull, but detectable As forms in rice straws and soils increased with increasing ROX dose. Grain As(III) was unrelated to ROX dose but exceeded the Chinese rice As limit (0.15mgAs(III)kg(-1)). Dietary ROX enhanced straw As(III) mostly, with the slope of 0.020, followed by hull DMA (0.006) and grain DMA (0.002). The slopes of soil As(V) and As(III) were 0.003 and 0.001. This is the first report illustrating the quantitative delivery of ROX via food chain, which helps to evaluate health and environmental risks caused by ROX use in animal production.

Phosphate enhances uptake of As species in garland chrysanthemum (C. coronarium) applied with chicken manure bearing roxarsone and its metabolites.

Roxarsone (ROX), a world widely used feed organoarsenic additive in animal production, can be excreted as itself and its metabolites in animal manure. Animal manure is commonly land applied with phosphorous (P) fertilizer to enhance the P phytoavailability in agriculture. We investigated the accumulation of As species in garland chrysanthemum (C. coronarium) plants fertilized with 1% (w/w, manure/soil) chicken manure bearing ROX and its metabolites, plus 0, 0.05, 0.1, 0.2, 0.4, and 0.8 g P2O5/kg, respectively. The results show that As(III) was the sole As compound in garland chrysanthemum shoots, and As(III) and As(V) were detectable in roots. Elevated phosphate level supplied more As(V) for garland chrysanthemum roots through competitive desorption in rhizosphere, leading to significantly enhanced accumulation of As species in plants. As(III) was the predominant As form in plants (85.0∼90.6%). Phosphate could not change the allocation of As species in plants. Hence, the traditional practice that animal manure is applied with P fertilizer may inadvertently increase the potential risk of As contamination in crop via the way ROX → animal → animal manure → soil → crop.

Roxarsone and its metabolites in chicken manure significantly enhance the uptake of As species by vegetables.

Roxarsone is an organoarsenic feed additive which can be finally degraded to other higher toxic metabolites after excreted by animal. In this work, the uptake of As species by vegetables treated with chicken manure bearing roxarsone and its metabolites was investigated. It was showed that more than 96% of roxarsone added in chicken feed was degraded and converted to arsenite, monomethylarsonic acid, dimethylarsinic acid, arsenate, 4-hydroxyphenylarsonic acid and other unknown As species. Arsenite and arsenate could be found in roots of vegetables but only arsenite transported up to shoots. Chicken manure bearing roxarsone and its metabolites increased 33-175% of arsenite and 28% ∼ seven times of arsenate in vegetable roots, 68-175% of arsenite in edible vegetable shoots. Arsenite, the most toxic As form, was the major extractable As species in vegetables accounted for 79-98%. The results reflected that toxic element As could be absorbed by vegetables via the way: roxarsone in feed → animal → animal manure → soil → crop and the uptake of As species would be enhanced by using chicken manure bearing roxarsone and its metabolites as organic fertilizer.

External inorganic N source enhances the uptake of As species in garland chrysanthemum (C. coronarium) amended with chicken manure bearing roxarsone and its metabolites.

Roxarsone (ROX), a widely used feed organoarsenic additive, is excreted as itself and its metabolites in animal manure. Animal manure is commonly applied with N fertilizer to meet the N demand of crop. We investigated the accumulation of As species in garland chrysanthemum plants fertilized with chicken manure (CM) bearing ROX and its metabolites, combined with different inorganic N sources (NH4(+), NO3(-) and urea), respectively. The change of pH, N forms and As species in soils was examined as well. The results show that As(V), As(III) and dimethylarsinic acid (DMA) were detectable in soils, and conversions between As species were affected by three inorganic N sources, irrespective of N form and soil pH. As(III) was the sole As species in garland chrysanthemum shoots, and As(III) and As(V) could be detected in roots. Urea, superior to NH4(+), significantly enhanced the uptake of As species in plants by promoting plant growth, while NO3(-) slightly reduced the As accumulation due to decreased biomass. As(III) was the dominant As compound (86.9-89.7%) in plants. Therefore, inorganic N fertilizers may inadvertently increase the risk of As contamination in plant from ROX via the way ROX→chicken→CM→soil→crop.

[Investigation of As, Cu and Zn species and concentrations in animal feeds].

Seventy chicken and seventy-six pig feeds were collected from the feed stores in Guangdong province, and the species and concentrations of As, Cu and Zn were determined. We also examined the stability of roxarsone (ROX), one of the most widely used organoarsenical additives, either in the additive or in the feed at room temperature. The results showed that, averagely, the chicken and pig feeds contained 3.6 and 6.5 mg.kg-1 (As), 18.2 and 119.4 mg.kg-1 (Cu),and 124.6 and 486.2 mg.kg-1 (Zn), respectively. The excessive dosages of As, Cu and As in animal feeds will lead to higher residue of As, Cu and Zn in animal manures. Based on the national limit criteria for feed or feed additive, it was supposed that organoarsenicals had been used, only few feed samples exceeded the As limit, however, the excessive Cu and Zn in pig feeds were much more common. Organoarsenicals were found in 25.4% of the total feed samples, and As(Ill) and As(V) were the two most commonly detected As impurities in feeds bearing organoarsenicals. The mean detectable ROX and arsenilic acid were 7.0 and 21.2 mg.kg-1, respectively. Organoarsenicals were detectable in 24. 3% of the chicken feed samples and 26. 3% of the pig feed samples. Moreover, ROX was commonly used in chicken feeds, while p-ASA in pig feeds. ROX and the inorganic As impurities, either in the commercial additive or in the feed, remained stable for at least 30 days at room temperature, indicating the higher As impurities in feeds probably originated from the As impurities in organoarsenical additives. This is a new As exposure pathway for the producer and user of organoarsenicals and feeds amending organoarsenicals.

Occurrence of arsenic impurities in organoarsenics and animal feeds.

Organoarsenics are widely used as excellent feed additives in animal production in the world. Roxarsone (ROX) and arsanilic acid (ASA) are two organoarsenics permitted to be used in China. We collected 146 animal feed samples to investigate the appearance of ROX, ASA, and potential metabolites, including 3-amino-4-hydroxyphenylarsonic acid (3-A-HPA), 4-hydroxyphenylarsonic acid (4-HPA), As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in feeds. The stability of ROX in both ROX additives and animal feeds was also examined. The results show that 25.4% of the 146 animal feeds contained organoarsenics, with average contents of ROX and ASA as 7.0 and 21.2 mg of As/kg, respectively. Unexpectedly, As(III) and MMA frequently occurred as As impurities in feeds bearing organoarsenics, with higher contents than organoarsenics in some samples. 3-A-HPA, 4-HPA, and DMA were not detected in all samples. ROX and As impurities in both ROX additives and feeds stayed unchanged in the shelf life. It suggests that As impurities in animal feeds bearing organoarsenics should generate from the use of organoarsenics containing As impurities. This constitutes the first report of As impurities in organoarsenics.

Uptake and transport of roxarsone and its metabolites in water spinach as affected by phosphate supply.

Roxarsone (ROX) is widely used as a feed additive in intensive animal production. While an animal is fed with ROX, the As compounds in the manure primarily occur as ROX and its metabolites, including arsenate (As[V]), arsenite (As[III]), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). Animal manure is commonly land applied with phosphorous fertilizers in China. A pot experiment was conducted to investigate the phytoavailability of ROX, As(V), As(III), MMA, and DMA in water spinach (Ipomoea aquatica), with the soil amended with 0, 0.25, 0.50, 1.0, and 2.0 g PO(4)/kg, respectively, plus 2% (w/w manure/soil) chicken manure (CM) bearing ROX and its metabolites. The results indicate that this species of water spinach cannot accumulate ROX and MMA at detectable levels, but As(V), As(III), and DMA were present in all plant samples. Increased phosphorous decreased the shoot As(V) and As(III) in water spinach but did not affect the root As(V). The shoot DMA and root As(III) and DMA were decreased/increased and then increased/decreased by elevated phosphorous. The total phosphorous content (P) in plant tissue did not correlate with the total As or the three As species in tissues. Arsenate, As(III), and DMA were more easily accumulated in the roots, and phosphate considerably inhibited their upward transport. Dimethylarsinic acid had higher transport efficiency than As(V) and As(III), but As(III) was dominant in tissues. Conclusively, phosphate had multiple effects on the accumulation and transport of ROX metabolites, which depended on their levels. However, proper utilization of phosphate fertilizer can decrease the accumulation of ROX metabolites in water spinach when treated with CM containing ROX and its metabolites.

[Pesticide residual status in litchi orchard soils in Guangdong, China].

Litchi is a famous tropical and subtropical fruit originated in South China. Guangdong is one of the most important litchi production areas in China. Two hundred and eight soil samples were collected in litchi orchards after harvesting the fruit, in which nine often-used pesticides including metalaxyl, mancozeb, carbendazim, deltamethrin, cypermethrin, cyhalothrin, dipterex, dimethoate and dichlorvos were detected. The results showed that the detectable rates of various pesticides were ranked cypermethrin (59.1%) > carbendazim (51.0%) > mancozeb (11.1%) > metalaxyl (6.7%) > cyhalothrin (3.4%). Dimethoate and dichlorvos were detectable in few soil samples, and deltamethrin and dipterex were undetectable in all samples. The percentages of soil samples where different pesticides could be detected in one sample followed the order: one pesticide detectable (40.4%) > two pesticides simultaneously detectable (31.3%) > pesticide undetectable (18.8%) > three pesticides simultaneously detectable (8.2%) > four pesticides simultaneously detectable (1.4%). The concentrations of mancozeb in detectable samples averaged 39.05 microg x kg(-1), and that of cypermethrin was 7.83 microg x kg(-1). The mean concentrations of the other five pesticides ranged from 0.19 microg x kg(-1) to 1.65 microg x kg(-1). Totally, the pesticide residue status in litchi orchards in Guangdong was venial.

Arsenic uptake by two vegetables grown in two soils amended with As-bearing animal manures.

Organoarsenicals are widely used as growth promoters in animal feed, resulting in unabsorbed arsenic (As) left in animal manures. A pot experiment was conducted to investigate the growth and As uptake of amaranth (Amaranthus tricolor Linn, a crop with an axial root system) and water spinach (Ipomoea aquatica Forsk, a crop with a fibrous root system) grown in a paddy soil (PS) and a lateritic red soil (LRS) amended with 2% and 4% (w/w) As-bearing chicken manure and pig manure, respectively. Soils without any fertilizers were the controls. The biomass, As contents and total As uptake of the shoots, As transfer factors (TFs) from roots to shoots and the root/shoot (R/S) ratios of water spinach were significantly higher than those of amaranth (p<0.0015). The biomass, total As uptake and R/S ratios showed significant difference for soil types (p<0.0031). Manure amendments increased the biomass of both vegetables, reduced the As contents in amaranth but increased those in water spinach. The As contents were negatively correlated with the biomass in amaranth, but positive correlation was observed for water spinach. The total As uptake by amaranth was decreased in PS and insignificantly affected in LRS by manure application, but that by water spinach was significantly increased in both soils. We suggest that the higher As uptake by water spinach might be related to its root structure and R/S ratio. Heavy application of As-bearing animal manures should be avoided in water spinach.

[Bioavailability of As, Cu and Zn in two soils as affected by application of chicken manure and pig manure].

Animal manures contain higher As, Cu and Zn since organoarsenicals, copper and zinc additives are widely used in modern intensive animal production. A pot experiment in water spinach was conducted to investigate As, Cu and Zn bioavailability in a paddy soil (PS) and a lateritic red soil (LRS) applied with 2% and 4% (mass fraction) chicken manure (CM) and pig manure (PM), respectively. Soils without any fertilizer were included as the checks (CK). The results show that nearly all treatments with manures significantly increase the biomass of the above-ground part of water spinach compared to the CK. The biomass in PS is significantly greater than that in LRS. The As concentrations and uptake rates of water spinach are significantly enhanced by manure application, showing the rule of higher rates > lower rates, PM > CM and in PS> in LRS. Except for the Cu concentrations in PS, manure application significantly increases the Cu, Zn concentrations and uptake rates as well. Soil total As in all treatments slightly reduce, available As and percents of available As over total As (PAs) considerably decrease after the harvest of water spinach, but total Cu, Zn and available Cu, Zn and percents of available Cu and Zn over total Cu and Zn (PCu and PZn) nearly in all manure-amended treatments increase. Soil total As increases by 0.3-3.0 mg x kg(-1), available As by 0.011-0.034 mg x kg(-1), the PAs by 0.033-0.178 percentage points in all treatments with manures, as compared to the CK. Soil total Cu, available Cu and the PCu increases by 3.1-30.4 mg x kg(-1), 5.2-19.4 mg x kg(-1) and 1.2-34.1 percentage points, respectively. Those of Zn increase by--10.6-79.6 mg x kg(-1), 4.0-65.9 mg x kg(-1) and 1.0-64.2 percentage points. We assume that the bioavailability of soil heavy metals be evaluated by the increment of available concentration and percent available concentration over total concentration, higher rate manure application improves the bioavailability of soil As, Cu and Zn than lower rate one and in LRS than in PS.

[Yield and heavy metal content of Brassica parachinensis influenced by successive application of chicken manure].

High heavy metal content in animal manures commonly occurs in the world since microelement additives are widely used in intensive animal production. Successive field trials in Brassica parachinensis (BP) were conducted to investigate the influence of successive application of chicken manure (at the rate of) on the yield and heavy metal content of BP. The application rate of chicken manure was calculated by its N content and ranged from N 0-450 kg x hm(-2). The results indicate that compared to single application of inorganic fertilizers, chicken manure decreases the yield of BP in the first and the third crop, increases that in the second crop. Combinations of chicken manure and inorganic fertilizers increase the yield in the fourth yield. Mean yields of all treatments in various crops are greatly different. The second crop is significantly higher than all other crops. In terms of mean heavy metal contents of BP of four crops in various treatment, As and Zn contents increase with applying chicken manure, Cr and Cd contents decrease, Pb contents don't change considerably, and Cu contents increase with applying chicken manure and inorganic fertilizers together. Generally, except for the second crop, mean As, Pb, Cr, Cu and Zn contents of BP in various crops increase with the increasing application times of chicken manure, mean Cd contents decrease. Hence, mass application for one crop or repeated application of chicken manure should be avoided in crop production.