A chloride efflux transporter,BIG RICE GRAIN 1, is involved in mediating grain size and salt tolerance in rice

Grain size is determined by the size and number of cells in the grain. The regulation of grain size is crucial for improving crop yield; however, the genes and molecular mechanisms that control grain size remain elusive. Here, we report that a member of the detoxification efflux carrier /Multidrug and Toxic Compound Extrusion (DTX/MATE) family transporters, BIG RICE GRAIN 1 (BIRG1), negatively influences grain size in rice (Oryza sativa L.). BIRG1 is highly expressed in reproductive organs and roots. In birg1 grain, the outer parenchyma layer cells of spikelet hulls are larger than in wild-type (WT) grains, but the cell number is unaltered. When expressed in Xenopus laevis oocytes, BIRG1 exhibits chloride efflux activity. Consistent with this role of BIRG1, the birg1 mutant shows reduced tolerance to salt stress at a toxic chloride level. Moreover, grains from birg1 plants contain a higher level of chloride than those of WT plants when grown under normal paddy field conditions, and the roots of birg1 accumulate more chloride than those of WT under saline conditions. Collectively, the data suggest that BIRG1 in rice functions as a chloride efflux transporter that is involved in mediating grain size and salt tolerance by controlling chloride homeostasis.     

Effective methods for isolation and purification of extracellular vesicles from plants

Plant extracellular vesicles (EVs) play critical roles in the cross-kingdom trafficking of molecules from hosts to interacting microbes, most notably in plant defense responses. However, the isolation of pure, intact EVs from plants remains challenging. A variety of methods have been utilized to isolate plant EVs from apoplastic washing fluid (AWF). Here, we compare published plant EV isolation methods, and provide our recommended method for the isolation and purification of plant EVs. This method includes a detailed protocol for clean AWF collection from Arabidopsis thaliana leaves, followed by EV isolation via differential centrifugation. To further separate and purify specific subclasses of EVs from heterogeneous vesicle populations, density gradient ultracentrifugation and immunoaffinity capture are then utilized. We found that immunoaffinity capture is the most precise method for specific EV subclass isolation when suitable specific EV biomarkers and their corresponding antibodies are available. Overall, this study provides a guide for the selection and optimization of EV isolation methods for desired downstream applications.     

Structure of plant photosystem I−light harvesting complex I supercomplex at 2.4 Å resolution

Photosystem I (PSI) is one of the two photosystems in photosynthesis, and performs a series of electron transfer reactions leading to the reduction of ferredoxin. In higher plants, PSI is surrounded by four light-harvesting complex I (LHCI) subunits, which harvest and transfer energy efficiently to the PSI core. The crystal structure of PSI-LHCI supercomplex has been analyzed up to 2.6 Å resolution, providing much information on the arrangement of proteins and cofactors in this complicated supercomplex. Here we have optimized crystallization conditions, and analyzed the crystal structure of PSI-LHCI at 2.4 Å resolution. Our structure showed some shift of the LHCI, especially the Lhca4 subunit, away from the PSI core, suggesting the indirect connection and inefficiency of energy transfer from this Lhca subunit to the PSI core. We identified five new lipids in the structure, most of them are located in the gap region between the Lhca subunits and the PSI core. These lipid molecules may play important roles in binding of the Lhca subunits to the core, as well as in the assembly of the supercomplex. The present results thus provide novel information for the elucidation of the mechanisms for the light-energy harvesting, transfer and assembly of this supercomplex.     

Potassium and phosphorus transport and signaling in plants

Nitrogen(N), potassium(K), and phosphorus(P) are essential macronutrients for plant growth and development, and their availability affects crop yield. Compared with N, the relatively low availability of K and P in soils limits crop production and thus threatens food security and agricultural sustainability. Improvement of plant nutrient utilization efficiency provides a potential route to overcome the effects of K and P deficiencies. Investigation of the molecular mechanisms underlying how plants sense, absorb, transport, and use K and P is an important prerequisite to improve crop nutrient utilization efficiency. In this review, we summarize current understanding of K and P transport and signaling in plants, mainly taking Arabidopsis thaliana and rice(Oryza sativa) as examples. We also discuss the mechanisms coordinating transport of N and K, as well as P and N.     

Genomes of 12 fig wasps provide insights into the adaptation of pollinators to fig syconia

Figs and fig pollinators are one of the few classic textbook examples of obligate pollination mutualism. The specific dependence of fig pollinators on the relatively safe living environment with sufficient food sources in the enclosed fig syconia implies that they are vulnerable to habitat changes. However, there is still no extensive genomic evidence to reveal the evolutionary footprint of this long-term mutually beneficial symbiosis in fig pollinators. In fig syconia, there are also non-pollinator species. The non-pollinator species differ in their evolutionary and life histories from pollinators. We conducted comparative analyses on 11 newly sequenced fig wasp genomes and one previously published genome. The pollinators colonized the figs approximately 66.9 million years ago, consistent with the origin of host figs. Compared with nonpollinators, many more genes in pollinators were subject to relaxed selection. Seven genes were absent in pollinators in response to environmental stress and immune activation. Pollinators had more streamlined gene repertoires in the innate immune system, chemosensory toolbox, and detoxification system. Our results provide genomic evidence for the differentiation between pollinators and nonpollinators. The data suggest that owing to the long-term adaptation to the fig, some genes related to functions no longer required are absent in pollinators.     

Morphology and Genetic Diversity of Phragmites australis in Beijing

为探明北京地区芦苇(Phragmites australis)的资源状态和多样性, 实地考察北京主要河流、湿地和水库, 发现北京地区芦苇总生长面积已超过600 hm²。芦苇染色体倍性以八倍体为主, 四倍体次之。在面积较大的湿地内, 八倍体单一芦苇群落占据优势地位; 而在城市的浅河内有形态和遗传性多样的混合种群。研究表明, 植物性状和倍性水平之间无显著相关性。在小清河发现了6种形态各异的芦苇克隆, 均属于叶绿体DNA片段的P单倍型; 其单倍体基因组大小为(0.499±0.019) pg, 变异系数为3.8%。这表明表型与单倍型之间也不具相关性。此外, 发现1个具有变叶特性的芦苇, 将其命名为金条芦苇。北京地区芦苇形态和遗传多样性为研究芦苇基因型与环境适应性之间的关系提供了珍贵的资源。     

Effects of Deficit Irrigation on the Photosynthetic and Physiological Characteristics of Leaves and Yield of Isatis tinctoria

以北板蓝根(Isatis tinctoria)为研究对象, 于2018年在河西走廊中部干旱绿洲开展水分控制试验, 设轻、中、重度亏水及充分供水4个控水水平, 通过大田试验探究膜下滴灌条件下亏缺灌溉对板蓝根叶片生理指标、灌水量及产量的影响, 为河西地区板蓝根灌溉策略的制定提供理论依据。结果表明, 板蓝根叶片净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)因营养和肉质根生长期受到亏缺灌溉影响而显著下降, 降幅随亏水程度的加剧而增大, 轻度亏水处理对叶片光合能力的影响不显著, 且在复水之后存在一定的补偿响应; 轻度亏水处理的产量与对照(8 348.91 kg·hm^-2)相比无显著差异, 而其它处理的产量均有不同程度的下降; 灌水量与产量的拟合关系呈二次抛物线, 即产量不随灌水量的增加而升高。因此, 综合分析表明膜下滴灌调亏降低了板蓝根叶片的光合能力, 而营养生长期轻度亏缺灌溉可以节水并提高产量和灌溉效率。     

家蝇Phormicin A多克隆抗体的制备及效价检测

家蝇Phormicin作为防御素家族的成员,是一类具有广普抗菌活性的抗菌肽.本研究采用原核表达法表达并纯化获得了家蝇PhormicinA蛋白.将家蝇Phormicin A原核表达蛋白与完全佐剂和不完全佐剂乳化混匀,先后免疫新西兰白兔获得其多克隆抗体.通过原核表达蛋白中和吸附实验,以及Western blot实验验证了抗体的特异性.进一步用金黄色葡萄球菌刺激家蝇三龄幼虫样品,进行内源性验证并测定抗体的效价.结果 显示,该多克隆抗体既可以识别家蝇Phormicin A原核表达蛋白,也可以识别金黄色葡萄球菌刺激家蝇三龄幼虫产生的内源性Phormicin A蛋白.本研究为进一步探索Phormicin在家蝇天然免疫和防御中的机制等后续工作打下基础.     

β-1,6葡聚糖酶前体编码基因Ss4p对甘蔗黑穗病菌分泌蛋白组的影响

甘蔗(Saccharum spp.)是世界也是中国主要的糖料作物.由甘蔗黑穗病菌(Sporisorium scitamineum)引起的甘蔗黑穗病是中国甘蔗生产上最主要的病害,每年造成重大损失.分泌蛋白在真菌侵染寄主植物与获取营养及病理过程起重要作用.本实验室在分析甘蔗黑穗病菌基因组与转录组数据时,发现1个与真菌细胞壁降解有关的β-1,6葡聚糖酶前体的基因Ssa4p.为了揭示Ssa4p对甘蔗黑穗病菌致病性和分泌蛋白组的影响,本研究利用CRISPR/Cas9和T-DNA双元载体所构建的甘蔗黑穗菌基因敲除系统,成功获得了Ssa4p基因的失活突变株.ΔSsa4p突变株(Δ35-Ssa4p)与野生型菌株JG36的配合能力降低且致病性减弱.用iTRAQ方法对Δ35-Ssa4p和野生型菌株的分泌蛋白组进行比较分析,共鉴定到蛋白质1430个,其中上调差异表达蛋白质685个,下调差异表达蛋白质745个.GO功能富集分析及KEGG分析表明,差异蛋白主要定位于无膜细胞器和核糖体,其功能包括参与核糖体、氨基糖和核苷酸糖代谢等生物学过程.本研究发现β-1,6葡聚糖前体影响植物病原真菌的分泌蛋白,加深了对真菌致病性调控机制的认识.