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Highlights • Four GWAS-identified loci in Alzheimer's disease don't contribute to PD, ALS, and MSA risk in a Chinese population. • Rs28834970 in the PTK2B gene may modulate the phenotype of cognitive function in PD. • No significant differences were found in MAFs between these variants and the different subgroups in different diseases. Abstract Background A number of genetic variants have previously been identified and associated with the risk of Alzheimer's disease (AD), including rs10838725 in CELF1 , rs28834970 in PTK2B , rs17125944 in FERMT2, and rs10410544 in SIRT2 based on genome-wide association studies. Considering the overlap between the clinical manifestation and pathological characteristics of AD and Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and multiple system atrophy (MSA), we conducted a large sample study to investigate the associations between these variants and these three common neurodegenerative diseases in a Chinese population. Methods A total of 2449 patients, including 1219 PD, 870 sporadic ALS, and 360 MSA, and 821 healthy controls were examined for this study. All cases were genotyped for single-nucleotide polymorphisms using Sequenom iPLEX assay technology. Results No significant differences were found in genotype distribution and minor allele frequencies between the four candidate variants and the three neurodegenerative diseases. However, a significant difference was found in the minor allele frequency of rs28834970 in PTK2B between PD patients with normal and abnormal cognitive function (p = 0.001). Moreover, the minor allele "C" was associated with an increased risk for cognitive impairment in PD (OR = 1.84). Although this observation was not significant (p = 0.064), the mean Addenbrooke's Cognitive Examination-Revised (ACER) score of PD patients with the risk allele of rs28834970 was 2.913 ± 1.569 points lower than that of PD patients without the risk allele. Conclusion This study provides new insight into some of the phenotypes that may share the common pathogenesis of different neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Remobilization of leaf nitrogen (N) contributes greatly to grain N in maize, but leads to low photosynthetic rate (P n ). P n is determined by various N components involving in light harvest and CO 2 reduction. However, it is less clear which N component is the major contributor for the reduction of photosynthesis in modern stay-green maize hybrids. In this study, we analyzed the relationship between remobilization of different N components and P n during grain filling stage under low N (no N application) and high N (180 kg N ha −1 ) in a field experiment. The remobilization efficiency of photosynthetic enzymes (PEPc, PPDK and Rubisco) in the leaf was much higher than that of thylakoid N and other N components. Low N supply increased the remobilization efficiency of all the leaf N components. During grain filling stage, the amount of all the N components decreased together with P n . The ratio of P n to the N in the PEPc, PPDK and Rubisco kept increase in the whole grain filling stage, while the ratio of P n to chlorophyll and thylakoid-N decreased. Correlation analysis indicated that P n was more related to the content of photosynthetic enzymes than to chlorophyll and thylakoid N. It is concluded that photosynthetic enzymes serve as an N storage reservoir at early grain filling stage and their degradation is critical in the reduction of P n during later grain filling stage. Future breeding targets may be focused on enhancing the efficiency of photosynthetic enzymes during late grain filling stage. [ABSTRACT FROM AUTHOR]

One strategy for plants to adapt to low nitrogen is to reduce shoot growth and allocate more nitrogen and carbon for root growth. The mechanism underlying the response of leaf growth to low-nitrogen remains unknown. In this study, we investigated cell division and elongation in maize leaf growth in response to low-nitrogen by using an integrated approach. Kinematic analysis revealed that low-nitrogen inhibited leaf elongation mainly by shortening length of division zone, reducing cell flux and elemental growth rate. Hormone analysis revealed that changes of gibberellins caused by low-nitrogen correlate with the observed changes in division zone size and elemental growth rate in response to low-nitrogen, suggesting role of gibberellin in low-nitrogen induced inhibition of leaf elongation. RNA-Seq identified that GA20ox4 (GRMZM2G060940), a key enzyme for synthesis of gibberellins, was down-regulated in both division and elongation zone of leaf under low-nitrogen supply. Furthermore, exogenous GA 3 application on low-nitrogen plants restored leaf growth. However, application of gibberellin biosynthesis inhibitor reduced leaf growth. It is concluded that low-nitrogen reduces cell flux and elemental growth rate in maize leaf via reducing gibberellin synthesis. As a result, leaf elongation rate was slower and leaf area was smaller, freeing nitrogen for export to roots. [ABSTRACT FROM AUTHOR]

In order to understand the regulation of source-sink relationship on leaf senescence in maize, we investigated the effect of pollination prevention on leaf senescence, post-silking dry matter and nitrogen accumulation and remobilization in different vegetative organs in one landrace and ten representative maize hybrids released between 1973 and 2000 in China. When pollination was prevented by covering silk with paper bags at silking stage, leaf senescence of Nongda 60, Yedan 13, Shendan 7 and Zhengdan 958 was delayed as shown by the remaining green leaf area per plant at maturity. However, pollination-prevention did not have obvious effect on the leaf senescence of Baimaya, Danyu 6, Yedan 2 and Xianyu 335. By contrast, pollination-prevention accelerated the leaf senescence of maize hybrids Zhongdan 2, Danyu13 and Yedan 4. It was found that leaf senescence of the late-released (since 1985) Chinese hybrids tended to be delayed by pollination-prevention, except XY335. From silking to physiological maturity, nitrogen content increased in the stem (plus the sheath, cob, husk, and tassel) and root of the non-pollinated plants. However, there was still a net reduction in leaf nitrogen content. We also found that pollination-prevention reduced leaf nitrogen remobilization efficiency, with genotypic difference and variation between the two years of testing. The results suggested that the response of leaf senescence to pollination-prevention is at least partially due to the change of leaf nitrogen remobilization efficiency. Leaf senescence tended to be delayed if leaf nitrogen remobilization efficiency is highly reduced by pollination-prevention. [ABSTRACT FROM AUTHOR]

Genotypic difference in nitrogen responsiveness of maize grain yield has gained considerable attention, however, the underlying physiological mechanism is less understood. Leaf area and plant type are important factors determining biomass production, and both of them are regulated by nitrogen supply. The current research aims to assess whether high nitrogen responsiveness is related to leaf growth and plant type. A 2-year field experiment was conducted with three maize cultivars (BMY, ZD2 and ZD958) differing in nitrogen responsiveness under a wide range of nitrogen supply (0, 60, 120, 180 and 240 kg N ha-1). The links between grain yield, leaf area dynamics, leaf angle and orientation value, and radiation use efficiency were investigated. Nitrogen responsiveness, defined as yield increment per unit of increased nitrogen supply, was 8.3–29.1% higher in ZD958 compared with the other cultivars. The maximum grain yield of ZD958 was 21.4–74.6% higher than that of the other cultivars. With increasing nitrogen supply, the increments in maximum leaf area and linear growth rate of leaf area were greater in ZD958, which was positively correlated with grain yield. The interaction effect between cultivar and nitrogen supply was significant on leaf length, but not on leaf width. Across the combinations between cultivar and nitrogen supply, the variation in grain yield was explained by leaf length rather than leaf width. High nitrogen supply increased leaf angle and reduced leaf orientation value, so as to make the leaf more horizontally distributed. However, this change was less significant in ZD958, indicating that the plant type was more compact under high nitrogen supply in maize cultivars with high nitrogen responsiveness. Radiation use efficiency, defined as the slope of the linear relationship between above-ground biomass produced and cumulated intercepted photosynthetic active radiation (PAR) was 5.2–13.2% higher in ZD958 than that of BMY. In conclusion, with increasing nitrogen supply, the cultivars with fast leaf growth and compact plant type have higher conversion efficiency of intercepted PAR into the above-ground biomass and get higher grain yield. • Nitrogen increased leaf area to a larger extent in the maize cultivar with high N responsiveness. • A compact plant type contributed to high N responsiveness under high N supply. • Grain yield increased via gains in radiation use efficiency under high N supply. [ABSTRACT FROM AUTHOR]

The introduction of new hybrids and integrated crop-soil management has been causing maize grain yield to increase. However, less attention has been paid on the nutrient concentration of the grain; this aspect is of great importance to supplying calories and nutrients in the diets of both humans and animals worldwide. Increasing the retranslocation of nutrients from vegetative organs to grain can effectively increase the nutrient concentration of grain and general nutrient use efficiency. The present study involved monitoring the dynamic change of macro- and micronutrients in different organs of maize during the grain filling stage. In addition, the mobility of different elements and their contribution to grain nutrient content were evaluated in a 2-year experiment under low (LN, no N supplied) and high N (HN, 180 kg N ha −1 ) supply. Under HN supply, the net remobilization efficiency ( RE ) of the vegetative organs as a whole (calculated as nutrient remobilization amount divided by nutrient content at silking) of N, P, K, Mn, and Zn were 44%, 60%, 13%, 15%, and 25%, respectively. The other nutrients (Mg, Ca, Fe, Cu, and B) showed a net accumulation in the vegetative organs as a whole during the grain filling stage. Among the different organs, N, P, and Zn were remobilized more from the leaves ( RE of 44%, 51% and 43%, respectively) and the stalks (including leaf sheaths and tassels) ( RE of 48%, 71% and 43%, respectively). K was mainly remobilized from the leaves with RE of 51%. Mg, Ca, Fe, Mn, and Cu were mostly remobilized from the stalks with the RE of 23%, 9%, 10%, 42%, and 28%, respectively. However, most of the remobilized Mg, Ca, Fe, Mn, Cu, and Zn were translocated to the husk and cob, which seemingly served as the buffer sink for these nutrients. The RE s of all the nutrients except for P, K, and Zn were vulnerable to variations in conditions annually and were reduced when the grain yield and harvest index were lower in 2014 compared with 2013. Under LN stress, the RE was reduced in P and Zn in 2013, increased in Cu and unchanged in other nutrients. The concentration of these nutrients in the grain was either unchanged (P, K, Ca, Zn, and B) or decreased (N, Mg, Fe, Mn, and Cu). It is concluded that grain N, P, K, Mn, and Zn, but not Mg, Ca, Fe, Cu, and B concentration, can be improved by increasing their remobilization from vegetative organs. However, enhancing the senescence of maize plant via LN stress seems unable to increase grain mineral nutrient concentration. Genetic improvement aiming to increase nutrient remobilization should take into account the organ-specific remobilization pattern of the target nutrient. [ABSTRACT FROM AUTHOR]

Increasing the response of maize yield to nitrogen (N) application is essential for food security and economic benefits of the farmers. However, the physiological mechanism underlining N responsiveness is unclear. Three maize cultivars with different N-responsiveness, BMY (the low), ZD2 (the medium) and ZD958 (the high) were grown in the field under a wide range of N supply (from 0 to 240 kg N per ha) in two years. Plant growth rate, plant N uptake rate, ear growth rate and ear N allocation rate, and their relationship to grain yield formation were investigated during the early critical period (14 days before silking). The direct path coefficient of grain number to grain yield was 0.82, which explained 96% of the variation in grain yield (R2 = 0.91). There was not a trade-off between grain number and other yield components. ZD958 got more grains per ear than the other cultivars in response to N supplies. The variation in grain number was mostly explained by the number of floret primordia (57% for BMY, 93% for ZD2 and ZD958). When N supply increased from 0 to 240 kg N ha-1, ZD2 and ZD958 did not differ in nitrogen nutrition index, and were 7.2–32.8% higher than BMY. The number of grains and floret primordia was independent of plant growth rate and plant N uptake rate, although these rates increased with N supply. Ear growth rate and ear N allocation rate of ZD958 were higher compared with the other cultivars, especially under high N supply. Except BMY, the number of floret primordium and grain per ear depended on ear growth rate and ear N allocation rate. There was a positive correlation between ear growth rate and ear N allocation rate in ZD2 and ZD958. However, ear N allocation rate of BMY did not increase when its ear growth rate was greater than 19.2 mg oC-1. It is concluded that, with increasing N supply, N-responsive maize cultivars had high ear growth rate and allocated more N into the ear during the early critical period, which enhanced the differentiation of floret primordia, hence increasing grain number and final grain yield. • High N-responsiveness of grain yield depends on grain number per ear. • Genotypic variation in grains number is explained by floret primordium development. • Floret primordium number in response to N depends on ear growth and ear N allocation. [ABSTRACT FROM AUTHOR]

Efficient nitrogen (N) utilization is crucial for maintaining grain yield under low N input. Less is known about the role of within-plant N allocation and reallocation on ear development and the factors determining N allocation during the critical period around silking. In this study, two maize hybrids, ZD958 (N-efficient) and LY99 (N-inefficient), were evaluated in a 2-year field experiment under two N rates (60 and 180 kg N ha-1). N transport and allocation into the ear during critical period were investigated using 15N stable isotopic tracer. The number and area of vascular bundles in ear shank, above- and below-ear internode were measured. The two hybrids did not differ in grain yields under high N rate. However, the grain yield of ZD958 was 43.6% higher than that of LY99 under low N rate, deriving from 26.3% and 13.9% increment in grain number and grain weight, respectively. At early critical growth stage before silking, ZD958 increased allocation of soil-derived N to the ear by 225.2% compared with LY99 under low N rate. At late critical growth stage after silking, ZD958 increased allocation of soil-derived N and reallocation of vegetative-N to the ear by 45.5% and 116.6%, respectively, compared with LY99 under low N rate. As a result, ear growth rate and ear N content of ZD958 was 22.2% and 69.1% higher than that of LY99 at the end of critical period. During N allocation and N reallocation, the lower leaves were sacrificed and the N status of the ear leaf and upper leaves was mostly maintained to sustain photosynthesis. In the ear shank, flux rate and N concentration of the xylem sap in ZD958 were 53.1% and 32.5% greater at silking stage, and were 40.8% and 27.5% greater at 14-days after silking, respectively, compared with LY99 under low N rate. Correspondingly, the number and average area of big vascular bundles in ear shank of ZD958 were 56.2% and 31.0% greater compared with LY99. Parameters characterizing the number and area of big vascular bundles were positively correlated with N allocation and grain yield, while that of small vascular bundles were negative. It is concluded that efficient N allocation to the ear at critical period is essential for ear growth and the subsequent vegetative-N remobilization, so as to improve low-N tolerance in high-yielding maize hybrids. A superior vascular system around the ear, especially in the ear shank, can enhance N allocation into the ear and could be regarded as a physiological selection trait in maize breeding to improve nitrogen use efficiency. [Display omitted] • N-efficient cultivar developed more and heavier grains under low-N stress. • N-efficient cultivar allocated more soil-derived N to the ear before silking. • N-efficient cultivar reallocated more vegetative-N to the ear after silking. • Less N was allocated to and more N was reallocated from the lower leaves and stem. • A superior vascular system contributed to efficient N allocation and reallocation. [ABSTRACT FROM AUTHOR]

Root breeding has been proposed as a key factor in the “second green revolution” for increasing crop yield and the efficient use of nutrient and water resources. However, few studies have demonstrated that the genetic improvement of root characteristics directly contributes to enhancing nutrient-use-efficiency in crops. In this study, we evaluated the contribution of root growth improvement to efficient nitrogen (N) acquisition and grain yield under two different N-levels in a 3-year field experiment. We used two near-isogenic maize testcrosses, T-213 (large-root) and T-Wu312 (small-root), derived from a backcross of a BC 4 F 3 population from two parents (Ye478 and Wu312) with contrasting root size. We found that the root length density, root surface area, and dry weight at the silking stage were 9.6–19.5% higher in T-213 compared with the control T-Wu312. The root distribution pattern in the soil profile showed no significant differences between the two genotypes. The overall increase in root growth in T-213 enhanced post-silking N uptake, which increased grain yield by 17.3%. Correspondingly, soil nitrate concentrations in the >30 cm soil layer were reduced in T-213 under the high N treatment. These positive effects occurred under both adequate and inadequate N-supply and different weather conditions. Our study provides a successful case that increasing root size via genetic manipulation contributes directly to efficient N-uptake and higher yield. [ABSTRACT FROM AUTHOR]

A target in crop production is to simultaneously increase grain yield (GY) and grain nitrogen concentration (GNC). In maize, nitrogen (N) and genotype are two major factors affecting GY and GNC. Both N remobilization from vegetative tissues and post-silking N uptake contribute to grain N, but their relative contributions are genotype specific, and are affected by the N application rate. It is unclear whether the responses of GY and GNC to N application differ between genotypes with different post-silking N uptake and vegetative N remobilization characteristics. We investigated the effect of N application rate on post-silking N uptake, vegetative N remobilization, GY, and GNC of two high-yielding maize hybrids, ZD958 and XY335, which have contrasting N remobilization characteristics. We tested five N application rates (0, 60, 120, 180, 240 kg N ha −1 ) in a 4-year field study (from 2010 to 2013). There was a significant year × N × genotype interaction in the amount of vegetative N remobilization and N remobilization efficiency (NRE), and residual stalk N concentration at maturity. Compared with the low-NRE cultivar ZD958, XY335 showed the same GY but higher GNC because it had higher vegetative N remobilization, NRE but lower residual stalk N concentration under the favorable weather condition in 2010. The response of GNC to increasing N levels was the same between XY335 and ZD958 and was not affected by year conditions. The N level required to obtain the highest GY was the same in the two hybrids (156 ± 13 kg ha −1 and 159 ± 19 kg ha −1 ), but that required to obtain the highest GNC was greater in XY335 (216 ± 30 kg ha −1 ) than in ZD958 (195 ± 23 kg ha −1 ). From these results, we conclude that precise N fertilizer management as well as the selection of high-yielding hybrids with high NRE can increase GNC without negatively affecting GY or leading to surplus N storage in vegetative organs. [ABSTRACT FROM AUTHOR]

Producing more food with less input is imperative in feeding the increasing world population. Here, for the first time we characterize the multipartite responses of maize to nutrient-rich patches and demonstrate significant synergistic effects between root morphological and physiological responses on improving nutrient-use efficiency and yield. Our results showed that maize root length, lateral root formation, acid phosphatase (APase) secretion, and expression of ammonium transporter genes increased in the ammonium-containing patches; moreover, ammonium-induced rhizosphere acidification enhanced activity of APase. These root responses were associated with improved maize nutrition and growth even with reduced fertilizer input, suggesting an adaptive benefit of synergistic root foraging strategies. These new findings improve our understanding of root-foraging responses to nutrient-specific cues and are crucial for engineering root and rhizosphere properties to improve nutrient-use efficiency for sustainable crop production. • Producing more food with less input is imperative for sustainable intensification of agriculture. • Rhizosphere dynamics is key to controlling nutrient-use efficiency (NUE). • Localized nutrient-supply maximizes root/rhizosphere efficiency for improving NUE. • Harnessing root foraging provides a new approach for sustainable maize production. [ABSTRACT FROM AUTHOR]

Highlights: [•] Increasing GNC without GY penalty is a goal in modern maize breeding. [•] Selection of genotypes with high N and DM accumulation and high NRE is required. [•] Higher leaf PNUE is a possible way to maintain whole-plant photosynthesis under high NRE. [ABSTRACT FROM AUTHOR]

Abstract: The primary objective of this study was to better understand how root morphological alteration stimulates N uptake in maize plants after root growth restriction, by investigating the changes in length and number of lateral roots, 15NO3 − influx, the expression level of the low-affinity Nitrate transporter ZmNrt1.1, and proteomic composition of primary roots. Maize seedlings were hydroponically cultured with three different types of root systems: an intact root system, embryonic roots only, or primary roots only. In spite of sufficient N supply, root growth restriction stimulated compensatory growth of remaining roots, as indicated by the increased lateral root number and root density. On the other hand, there was no significant difference in 15NO3 − influx between control and primary root plants; neither in ZmNrt1.1 expression levels in primary roots of different treatments. Our data suggested that increased N uptake by maize seedlings experiencing root growth restriction is attributed to root morphological adaptation, rather than explained by the variation in N uptake activity. Eight proteins were differentially accumulated in embryonic and primary root plants compared to control plants. These differentially accumulated proteins were closely related to signal transduction and increased root growth. [Copyright &y& Elsevier]

Background Mutations in the leucine-rich repeat kinase 2 ( LRRK2 ) gene have been reported to be responsible for autosomal dominant late-onset sporadic Parkinson's disease (PD). The R1628P and G2385R polymorphisms of the LRRK2 gene have been identified as exclusively associated with PD in Asian populations, particularly in Han Chinese population. Considering that there is overlap of the clinical manifestations and pathological characteristics between PD and MSA, we studied the possible associations between R1628P and G2385R polymorphisms of the LRRK2 and MSA in a population of Han Chinese patients. Methods and patients A total of 318 MSA patients and 350 unrelated age- and sex-matched healthy controls (HCs) were included in the study. All subjects were genotyped for R1628P and G2385R using polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis and direct sequencing. Results No significant differences were observed in the genotype distribution and minor allele frequency (MAF) of R1628P between MSA patients and HCs ( P = 0.418 and P = 0.424), between MSA-C and HCs ( P = 0.347 and P = 0.353), between MSA-P and HCs ( P = 0.787 and P = 0.790), and between MSA-C and MSA-P ( P = 0.606 and P = 0.610). In addition, no significant differences were also observed in the genotype distribution and MAF of G2385R between MSA patients and HCs ( P = 0.141 and P = 0.051), between MSA-C and HCs ( P = 0.061 and P = 0.065), between MSA-P and HCs ( P = 0.184 and P = 0.158), and between MSA-C and MSA-P ( P = 0.354 and P = 0.853). Conclusion The present study suggests that R1628P and G2385R polymorphisms of the LRRK2 are not risk factors for MSA in the Han Chinese population. [ABSTRACT FROM AUTHOR]

• Stay-green maize cultivars differ in N allocation and remobilization under low-N stress. • Poor N allocation around silking limits young ear development and reduce floret primordia. • Poor vegetative-N remobilization exacerbates grain abortion and reduces grain weight. Nitrogen (N) efficient cultivars can achieve relatively high grain yield under reduced N input. Normally modern stay-green maize cultivars are high-yielding and more N efficient than the old senescent cultivars. However, less is known about the genotypic difference in N use efficiency (NUE) among stay-green high-yielding cultivars. This information is crucial for further genetic improvement in NUE of the modern stay-green cultivars. In the present study, two stay-green hybrids with different NUE, Zhengdan958 (ZD958, N-efficient) and Liangyu99 (LY99, N-inefficient), were grown under 60 (LN) and 180 kg N ha−1 (HN) conditions in a 4-year field experiment with split-design. The two hybrids did not differ in grain yield under HN. Under LN, grain yield and grain N content of LY99 was 23.6 % and 30.3 % lower compared to that of ZD958, respectively. LY99 had few grain number per row than ZD958. Correspondingly, floret primordia number decreased by 17.7 %, and grain abortion increased by 12.7 % in LY99 compared to ZD958. During critical period around silking, N concentration in the young ear of LY99 is lower than that in ZD958. Also, the maximum absolute ear growth rate and exponential duration of LY99 were 22.2 % and 6.0 % lower than that of ZD958 under LN, respectively. In LN conditions, the two hybrids did not differ in post-silking N accumulation. However, N remobilization from vegetative organs to grains in LY99 was 41.3 % lower than that in ZD935. In conclusion, NUE in stay-green cultivars could be improved by efficient N allocation into the young ear and vegetative-N remobilization during post-silking period under insufficient N supply. [ABSTRACT FROM AUTHOR]

• Genotypic differences in root Mn uptake, root-to-shoot Mn translocation and photosynthetic responses to Mn deficiency are observed in maize. • The metal transport genes are differentially expressed in the roots of contrasting genotypes with different tolerance to low-Mn. • Time-course of changes in Fv/Fm values in response to Mn deficiency provides a useful screening index for low-Mn tolerance. Deficiency of manganese (Mn) is a serious problem reducing crop yields on calcareous and sandy soils throughout the world. In maize, limited knowledge is available on genotypic differences in tolerance to low-Mn supply and the physiological mechanisms underlying this tolerance. In the present study we have evaluated twelve maize genotypes (inbred lines) for their tolerance to Mn deficiency. The evaluation was based on measurements of how low-Mn supply affected shoot biomass, leaf Mn concentrations, maximum quantum efficiency of photosystem II (F v /F m), photosynthetic net CO 2 assimilation, root length, Mn uptake and root-shoot Mn translocation. Tolerant genotypes were able to maintain optimum F v /F m values under a longer period of Mn deficiency with less reduction of foliar Mn concentration and photosynthetic rate, resulting in less reduction of shoot biomass, compared to sensitive genotypes. Efficient root uptake of Mn and root-to-shoot translocation of Mn also contributed to improved tolerance to Mn-deficiency. The metal transport genes YSL , NRAMP , ZIP , CAX and MTP , involved in root Mn uptake, root-to-shoot Mn translocation and vacuolar Mn homeostasis, were more highly expressed in the efficient genotype K22compared to sensitive genotype BY815. With respect to breeding of maize cultivars with improved Mn-efficiency, the time-course of changes in F v /F m values in response to Mn-deficiency provides a useful screening index for low-Mn tolerance. [ABSTRACT FROM AUTHOR]

• Low-N stress increases shoot-to-root auxin transport and increases auxin level in the root tip. • Higher auxin level in the root tip up-regulates cell wall acidification process which possibly accelerates cell elongation. • Higher auxin level in the root tip up-regulates TOR pathway which may accelerate cell division and/or cell elongation. Under low nitrogen (N) supply, an important adaption of the maize root system is to promote the root elongation so as to increase N uptake from a larger soil space. The underlying physiological mechanism is largely unknown. In the present study, two maize inbred lines (Ye478 and Wu312) were used to study the possible involvement of the auxin and target of rapamycin (TOR) pathway in low-N-induced root elongation. Compared to Wu312, primary root elongation of Ye478 was more sensitive to low nitrate supply. Correspondingly, more auxin was accumulated in the root tip, and more protons were secreted, increasing the acidity of the apoplast space. On the other hand, low-N-induced root elongation was greatly reduced when shoot-to-root auxin transport was inhibited by applying N-1-naphthylphthalamic acid (NPA) at the plant base or by pruning the top leaf where auxin is mostly synthesized. Furthermore, exogenous application of TOR inhibitor also eliminated the response of root elongation under low N. The content of TOR kinase and the expression of TOR pathway-related genes were significantly changed when shoot-to-root auxin transport was reduced by NPA treatment. Taken together, it is concluded that low-N stress increases shoot-to-root auxin transport which enhances root elongation via auxin-dependent acid growth and the auxin-regulated TOR pathway in maize. [ABSTRACT FROM AUTHOR]

Selection of high-yielding and nitrogen (N)-efficient cultivars under realistic agronomic conditions can benefit farmers in their production practices. In addition, phenotyping the root characteristics of high-yielding and N-efficient cultivars under N stress conditions is important to guide maize breeding for abiotic stress tolerance. The objective of this study was to (1) evaluate the potential increase in yield and reduction in required fertilizer input in maize cultivars, and (2) examine the root characteristics of high-yielding and N-efficient cultivars. Under the high-N (240 kg N ha−1) and the low-N (no N supplied) conditions, grain yield and nodal root traits of 10–67 dominant maize cultivars grown in North and Northeast China were investigated in field trials at six environments. The low-N conditions reduced grain yield by 24%, crown root number (CRN, shoot-borne roots formed at consecutive underground shoot nodes) by 8%, brace root number (BRN, shoot-borne roots formed at consecutive aboveground shoot nodes) by 44%, and brace root whorl number (BRWN, whorls of roots that arise from aboveground shoot nodes) by 50%. The grain yield showed a significant positive correlation with CRN and crown root length (CRL) under both N treatments. The cultivars were classified into four types based on the average grain yield under high-N and low-N treatments: EE, efficient under both high-N and low-N treatments; HNE, N efficient only under high-N treatment; LNE, N efficient only under low-N treatment; and NN, inefficient under both high-N and low-N treatments. The cultivars with EE and HNE types had 5%–10% greater grain yield and reduced N fertilizer input requirements by 11%–50%. Under the low-N conditions, the cultivars classified as EE and HNE types showed 4%–20% higher CRN and 14%–22% longer CRL compared with NN types. Cultivation of the EE and HNE maize cultivars in Northeast and North China may reduce N input requirements without compromising yield. Compared with NN type cultivars, the EE and HNE cultivars had greater CRN and CRL, which may be contributed to improving N acquisition and grain yield formation in response to N stress. [ABSTRACT FROM AUTHOR]

Recently, 17 new Parkinson's disease (PD) risk loci were identified in a genome-wide association studies meta-analysis in Caucasians; however, their association with PD in Chinese patients is largely unknown. Therefore, we performed a replication study of 5 of the most commonly identified candidate variants, including SORBS3 rs2280104, SCN3A rs353116, TOX3 rs4784227, GLAC rs8005172, and ZNF184 rs9468199, in a large sample of patients with PD (1506) and multiple system atrophy (MSA, 496) in a Chinese population. These 5 variants were found to not be associated with PD and MSA in the Chinese population. Our results suggest that these variants are not risk factors for PD or MSA in the Chinese population. [ABSTRACT FROM AUTHOR]

Abstract: Mutations in the sequestosome 1 gene (SQSTM1) have recently been identified in patients with amyotrophic lateral sclerosis, accounting for 1.11%–4.92% of familial ALS and 2.42%–4.37% of sporadic amyotrophic lateral sclerosis (SALS). The mutation spectrum of SQSTM1 in Chinese patients with SALS remains unknown. Three hundred and six patients with SALS from the Department of Neurology, West China Hospital of Sichuan University were recruited for this study. From the same region, 350 healthy individuals were recruited as a control group. The encoding regions of SQSTM1 were screened by direct sequencing. Three novel nonsynonymous mutations— p. I99L, p. D337E, and p. L341V—were identified in 3 patients with SALS, none of which were found in healthy controls. The male patient carrying mutation p. I99L presented limb symptom at age of 34 and died in 34 months. Two late-onset patients carrying D337E and p. L341V mutations had bulbar and limb onset, respectively. Moreover, a c.1166-14_1166-11delTACT mutation in the intron 7 was found in a living male patient with limb onset at age of 62. None of the patients carrying SQSTM1 mutation showed clinical evidence of concomitant Paget disease of bone or mutation of the valosin-containing protein gene. The mutation frequency of SQSTM1 was 0.98% in Chinese patients with SALS, which was lower than those in other racial populations. [Copyright &y& Elsevier]

Abstract: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with unknown pathophysiological mechanisms. Profilin 1 gene (PFN1) has been identified as a causative gene, which accounts for 1% to 2% of familial ALS. In this study, we investigated the mutation spectrum of PFN1 in Chinese patients with ALS. A total of 550 ALS patients (including 540 sporadic ALS [SALS] and 10 familial ALS) from the Department of Neurology, West China Hospital of Sichuan University, were recruited for the study. From the same region, 545 healthy control individuals (HC) were recruited as a control group. The encoding regions of the PFN1 gene were screened by direct sequencing. Novel candidate mutations or variations were confirmed by polymerase chain reaction-restriction fragment length polymorphism. A novel nonsynonymous p.R136W mutation was identified in an early-onset SALS female patient. A novel synonymous mutation p.L88L detected in a late-onset SALS female patient was considered nonpathogenic, as it was also detected in a control subject. No mutations were found in 10 familial ALS patients. Moreover, we found a significant difference in the genotype distribution of reported rs13204 (p.L112L) between SALS patients and HC (p = 0.0030). The frequency of minor allele ‘T’ of rs13204 in the SALS group was significantly lower than that in HC (p = 0.0040, OR = 0.7270, 95% CI = 0.5848–0.9039). Our results suggest that PFN1 mutation is an uncommon cause of ALS in the Han Chinese population. The SNP rs13204 of the PFN1 gene may have an important function in ALS development. The phenotype of ALS patients with mutantPFN1 gene varies among different genetic backgrounds. [Copyright &y& Elsevier]

Abstract: Recently, 5 single nucleotide polymorphisms (SNPs), rs2306677 in the inositol 1,4,5-triphosphate receptor 2 gene (ITPR2), rs1541160 in the kinesin-association protein 3 gene (KIFAP3), rs6690993 and rs6700125 in the FLJ10986 gene, and rs10260404 in the dipeptidyl-peptidase 6 gene (DPP6) have been reported to be associated with the risk of developing sporadic amyotrophic lateral sclerosis (SALS) in Caucasian populations. However, this association is not consistent among different studies and yet to be tested in Chinese SALS patients. We examined the above SNPs in a large cohort consisting of 395 SALS patients and 288 controls from Southwest China. Our results suggest that these SNPs are unlikely to be a common cause of SALS in Chinese populations. [Copyright &y& Elsevier]