Manganese deficiency in maize affects pollen viability

Maize (Zea mays L. cv. G2) was grown with 0.55 mg L^–1 (sufficient), or 0.0055 mg L^–1 (deficient) manganese in sand. Manganese-deficient plants developed visible deficiency symptoms and showed poor tasseling and delayed anther development. Compared to Mn-sufficient plants, Mn-deficient plants produced fewer and smaller pollen grains with reduced cytoplasmic contents. Manganese deficiency reduced in vitro germination of pollen grains significantly. Ovule fertility was not significantly affected by Mn. But in Mn-deficient plants seed-setting and development was reduced significantly.     

Fertilization and seed production with pollen from in-vitro-cultured maize tassels

Immature tassel meristems (1–1.5 cm) of maize (Zea mays L.) explanted to a defined nutrient medium underwent further growth and floral development. Microsporogenesis, gametogenesis and pollen maturation were completed within 25 d in vitro. The pollen, recovered from the cultured tassel, germinated on nutrient agar and also on receptive silks. Viable seed produced from controlled pollinations germinated and grew into mature, normal plants. Thus, a significant component of the life cycle of maize can be completed in vitro where analyses and manipulations are possible for both basic and applied research.     

Species-specific interaction of EA1 with the maize pollen tube apex

The egg apparatus-secreted polymorphic EA1 peptide is required for micropylar pollen tube (PT) guidance in maize, the last step of the PT journey during the double fertilization process in flowering plants. In a recent study we have shown that maize PTs are attracted in vitro by EA1 and that their growth is arrested at high peptide concentrations. Moreover, we have also shown that maize PTs are guided in vitro in a species-preferential manner to the micropylar opening of transgenic Arabidopsis ovules secreting the EA1-GFP fusion protein. In support of these findings, we have improved the ligand-receptor labeling assay and report here that the EA1 peptide interacts in vitro with the maize PT apex in a species-specific manner. Bound peptide gets internalized in large vesicles and is degraded. This finding indicates that the pollen tube remains sensitive to the attractant by its rapid internalization.     

Vertical variation in urticaceae airborne pollen concentration

The pollen contents at different heights (1.5 and 15 m) of species of the Urticaceae family have been studied by sampling with Hirst type volumetric samplers. In order to achieve this, the two pollen types belonging to this family have been treated separately,Urtica urens-Parietaria sp. on the one hand andUrtica membranacea on the other, the latter having a smaller pollen grain. The results show that meteorological factors are bound to influence the behaviour of both these types of pollen in relation to height. With damp weather the pollen contents vary very slightly at different heights while when the weather is dry and calm, differences in pollen content at different heights become more significant. Nevertheless, when the atmosphere is stratified, the behaviour of each pollen type is different. The results show that, for most of the months considered, there is a higher pollen content ofU. membranacea at upper heights, whileU. urens-Parietaria sp. has higher levels of pollen content at a lower height. High temperatures, absence of rain and calm weather conditions favour the presence of convective phenomena which in turn create a favourable atmosphere for the vertical transportation of the small pollen grains ofU. membranacea, which are better represented in the samplers placed at 15 m.     

Latitudinal variation in seed weight and flower number in Prunella vulgaris

Studies of seed-weight variation across altitudinal and latitudinal gradients have led to conflicting hypotheses regarding the selective value of this traint in relation to the length of the growing season. Growing-season length may also influence the evolution of seed number, and population differentiation in seed weight may be constrained by a negative genetic correlation between seed weight and seed number within populations. We examined variation in seed weight and an estimate of seed number (flower number) and the covariance of these traits among populations of Prunella vulgaris at five latitudes between northern Michigan and South Carolina. We measured seed weight and flower number in native habitats and in a common environment to determine the extent to which patterns observed in the field reflect genetic differentiation. We observed no genetically based variation in seed weight across the latitudinal gradient, although genetic variation among populations within a latitude was observed. In contrast to the lack of variation in seed weight, flower number increased clinally from northern Michigan to Tennessee in a common environment. Population mean flowering date in a common environment was successively later from north to south. Later-flowering individuals appear to achieve a larger size before flowering and consequently possess more resources for seed production. This difference may account for the greater flower production of late-flowering, southern populations. Independence of population mean seed weight and flower number across the latitudinal gradient suggests that population differentiation in seed weight has not been constrained by a trade-off between seed size and number within populations.     

Endogenous polyamine content during in vivo maturation and in vitro culture of maize pollen

Changes in polyamine content during in vivo maturation and in vitro culture of maize (Zea mays L.) pollen were studied. The endogenous content of free, conjugated and bound polyamines was analyzed during 30 days of pollen evolution, in both developmental pathways (microsporogenesis and androgenesis). The induction of androgenesis from cold-pretreated uninucleate pollen results, in most of cases, in a lower total polyamine content than that of the in vivo uninucleate pollen. These differences indicate that polyamine metabolism is altered during the induction of androgenesis, and this could be a consequence of increased polyamine assimilation. In general, pollen stages that involve cell division (tetrades, pre-anthesis pollen and four-day cultured pollen) are characterized by a predominance of free Spd. The increase of Spd and Spm in 15-day cultured pollen, when the first embryoids are formed, outline the possible implication of these polyamines in embryogenetic processes. Furthermore, these findings may contribute to the improvement of maize androgenesis yield, especially in recalcitrant genotypes, by the exogenous application of polyamines or polyamine-inhibitors to the culture medium.Abbreviations PAs polyamines - Put putrescine - Spd spermidine - Spm spermine - S free polyamine fraction - SH conjugated polyamine fraction - PH bound polyamine fraction     

空气花粉变化规律和预测预报研究进展

空气花粉是一个地区大气环境评估的重要指标,随着人们生态环境保护意识以及自身健康意识的提高,该领域的研究已经成为综合生物学、环境科学、气象学和医学等学科的全球性的研究课题.不同地区受其地理位置、植物组成和气候等多种因素的影响,空气花粉种类和浓度的变化模式有所不同,一般情况,一个地区白天空气花粉浓度高,夜晚浓度低;春夏季花粉浓度高,冬季花粉浓度低;春夏季乔木类植物花粉浓度高,而秋季草本类植物花粉浓度高.空气花粉预测预报工作直接关系到一个地区农业、环境、医疗卫生以及民众生活等多方面,当前空气花粉的预测预报工作已经由原来的定性预测发展到当前通过统计学和数学方法建立数学模型进行定量化预测,不仅可以进行空气花粉种类和浓度的预测,还可以通过花粉的变化预测未来气候的变化,预测的精确度也比以往有很大提高.通过分析空气花粉研究的进展对未来该领域的研究工作进行了展望.     

Natural variation of GmFATA1B regulates seed oil content and composition in soybean

Soybean (Glycine max) produces seeds that are rich in unsaturated fatty acids and is an important oilseed crop worldwide. Seed oil content and composition largely determine the economic value of soybean. Due to natural genetic variation, seed oil content varies substantially across soybean cultivars. Although much progress has been made in elucidating the genetic trajectory underlying fatty acid metabolism and oil biosynthesis in plants, the causal genes for many quantitative trait loci (QTLs) regulating seed oil content in soybean remain to be revealed. In this study, we identified GmFATA1B as the gene underlying a QTL that regulates seed oil content and composition, as well as seed size in soybean. Nine extra amino acids in the conserved region of GmFATA1B impair its function as a fatty acyl–acyl carrier protein thioesterase, thereby affecting seed oil content and composition. Heterogeneously overexpressing the functional GmFATA1B allele in Arabidopsis thaliana increased both the total oil content and the oleic acid and linoleic acid contents of seeds. Our findings uncover a previously unknown locus underlying variation in seed oil content in soybean and lay the foundation for improving seed oil content and composition in soybean.     

Diurnal variation of chosen airborne pollen at five sites in Poland

The aerobiological investigations were carriedout at five sites located in different climaticand geobotanical regions in Poland. The diurnalperiodicity of Alnus, Betula, Secale,Poaceae, Urtica, and Artemisia wasstudied during two successive years. The taxawere chosen on the basis of pollen grainabundance and allergenity. The pollen wascollected with a Burkard spore trap. Twelvetransversal transverses of microscope slidescorresponding to two-hour periods wereanalysed. The diurnal variations ofPoaceae, Alnus and Betula were irregularand varied between sites and years; highconcentrations were observed at different hoursof the day and night. Diurnal concentrations of Secale, Urtica and Artemisia hadonly one maximum in the middle of the day,constant between sites and years. The lowestconcentrations were observed between eveningand early morning. There was no close relationbetween the time of the liberation ofAlnus, Betula and Poaceae pollen and thetime of the maximum pollen counts. There was aseveral hour delay observed between the timeof Secale pollen liberation and maximumconcentration of airborne pollen.     

玉米潜在花粉源强计算模型的建立、改进与检验

潜在花粉源强是玉米花粉扩散模型的重要参数。为了确定玉米潜在花粉源强,本研究测定了逐日散粉量和逐时开花率,以此来确定逐时散粉量,作为模型中潜在花粉源强的输入值。以2009年溧水试验资料为基础,应用正态分布函数模拟逐时散粉量的日变化,通过气温和相对湿度参数订正逐时散粉量;利用2010年公主岭和溧水试验资料对玉米潜在花粉源强的正态分布模型进行检验。结果表明:公主岭试验中的"紫糯18"、"吉单35"和溧水试验中的"紫糯18"、"苏608"的逐时散粉量的模拟值与实测值之间的均方根误差分别为2.24×105、1.52×105、1.24×105和8.92×104粒·株-1,决定系数分别为0.330、0.545、0.365和0.606。利用相同的数据检验气温和相对湿度订正后的模型,各品种逐时散粉量的模拟值与实测值之间的均方根误差分别减少至1.25×105、9.03×104、5.14×104和4.22×104粒·株-1,决定系数则分别提高至0.656、0.718、0.779和0.843;模型效果明显改善,从而为进一步精确模拟玉米花粉扩散奠定基础。     

Identification and fine mapping of quantitative trait loci for the number of vascular bundle in maize stem

Studies that investigated the genetic basis of source and sink related traits have been widely conducted. However, the vascular system that links source and sink received much less attention. When maize was domesticated from its wild ancestor, teosinte, the external morphology has changed dramatically; however, less is known for the internal anatomy changes. In this study, using a large maize‐teosinte experimental population, we performed a high‐resolution quantitative trait locus (QTL) mapping for the number of vascular bundle in the uppermost internode of maize stem. The results showed that vascular bundle number is dominated by a large number of small‐effect QTLs, in which a total of 16 QTLs that jointly accounts for 52.2% of phenotypic variation were detected, with no single QTL explaining more than 6% of variation. Different from QTLs for typical domestication traits, QTLs for vascular bundle number might not be under directional selection following domestication. Using Near Isogenic Lines (NILs) developed from heterogeneous inbred family (HIF), we further validated the effect of one QTL qVb9‐2 on chromosome 9 and fine mapped the QTL to a 1.8‐Mb physical region. This study provides important insights for the genetic architecture of vascular bundle number in maize stem and sets basis for cloning of qVb9‐2.     

Effective number of pollen parents in clonal seed orchards

Summary A method for quantifying mating behavior in clonal seed orchards of forest tree species is presented. It involves the estimation of effective numbers of pollen parents from seed samples collected from individual ramets in such orchards. These effective numbers are variance effective numbers for populations of male gametes that are successful in uniting with ovules to produce viable seed. Three such effective numbers are defined for clonal seed orchards:N _p (a) for male gamete populations for ramets within clones,N _p (b) for male gamete populations for clones, andN _p (c) for male gamete populations for entire orchards. Estimators for these effective numbers and for standardized variances of allele frequencies in the male gametic populations are presented. Expressions are also given for the confidence intervals for each of the three effective numbers. Estimates of these parameters and the corresponding confidence intervals for two seed orchards are presented and interpreted.     

Natural variation of MS2 confers male fertility and drives hybrid breeding in soybean

A complete and genetically stable male sterile line with high outcrossing rate is a prerequisite for the development of commercial hybrid soybean. It was reported in the last century that the soybean male sterile ms2 mutant has the highest record with seed set. Here we report the cloning and characterization of the MS2 gene in soybean, which encodes a protein that is specifically expressed in the anther. MS2 functions in the tapetum and microspore by directly regulating genes involved in the biosynthesis of secondary metabolites and the lipid metabolism, which is essential for the formation of microspore cell wall. Through comparison of the field performance with the widely used male sterile mutants in the same genetic background, we demonstrated that the ms2 mutant conducts the best in outcrossing rate and makes it an ideal tool in building a cost-effective hybrid system for soybean.     

Zinc deficiency and pollen fertility in maize (Zea mays)

Zinc deficiency decreased pollen viability in maize (Zea mays L. cv. G2) grown in sand culture. On restoring normal zinc supply to zinc-deficient plants before the pollen mother cell stage of anther development, the vegetative yield of plants and pollen fertility could be recovered to a large extent, but the recovery treatment was not effective when given after the release of microspores from the tetrads. If zinc deficiency was induced prior to microsporogenesis it did not significantly affect vegetative yield and ovule fertility, but decreased the fertility of pollen grains, even of those which visibly appeared normal. If the deficiency was induced after the release of microspores from the tetrads, not only vegetative yield and ovule fertility but pollen fertility also remained unaffected.     

ABNORMAL POLLEN VACUOLATION1 (APV1) is required for male fertility by contributing to anther cuticle and pollen exine formation in maize

Anther cuticle and pollen exine are the major protective barriers against various stresses. The proper functioning of genes expressed in the tapetum is vital for the development of pollen exine and anther cuticle. In this study, we report a tapetum‐specific gene, Abnormal Pollen Vacuolation1 (APV1), in maize that affects anther cuticle and pollen exine formation. The apv1 mutant was completely male sterile. Its microspores were swollen, less vacuolated, with a flat and empty anther locule. In the mutant, the anther epidermal surface was smooth, shiny, and plate‐shaped compared with the three‐dimensional crowded ridges and randomly formed wax crystals on the epidermal surface of the wild‐type. The wild‐type mature pollen had elaborate exine patterning, whereas the apv1 pollen surface was smooth. Only a few unevenly distributed Ubisch bodies were formed on the apv1 mutant, leading to a more apparent inner surface. A significant reduction in the cutin monomers was observed in the mutant. APV1 encodes a member of the P450 subfamily, CYP703A2‐Zm, which contains 530 amino acids. APV1 appeared to be widely expressed in the tapetum at the vacuolation stage, and its protein signal co‐localized with the endoplasmic reticulum (ER) signal. RNA‐Seq data revealed that most of the genes in the fatty acid metabolism pathway were differentially expressed in the apv1 mutant. Altogether, we suggest that APV1 functions in the fatty acid hydroxylation pathway which is involved in forming sporopollenin precursors and cutin monomers that are essential for the development of pollen exine and anther cuticle in maize.