Jujube witches’ broom phytoplasmas inhibit ZjBRC1-mediated abscisic acid metabolism to induce shoot proliferation

Jujube witches’broom(JWB)phytoplasmas parasitize the sieve tubes of diseased phloem and cause an excessive proliferation of axillary shoots from dormant lateral buds to favour their transmission.In previous research,two JWB effectors,SJP1 and SJP2,were identified to induce lateral bud outgrowth by disrupting ZjBRC1-mediated auxin flux.However,the pathogenesis of JWB disease remains largely unknown.Here,tissue-specific transcriptional reprogramming was examined to gain insight into the genetic mechanisms acting inside jujube lateral buds under JWB phytoplasma infection.JWB phytoplasmas modulated a series of plant signalling networks involved in lateral bud development and defence,including auxin,abscisic acid(ABA),ethylene,jasmonic acid,and salicylic acid.JWB-induced bud outgrowth was accompanied by downregulation of ABA synthesis within lateral buds.ABA application rescued the bushy appearances of transgenic Arabidopsis overexpressing SJP1 and SJP2 in Col-0 and ZjBRC1 in the brc1-2 mutant.Furthermore,the expression of ZjBRC1 and ABA-related genes ZjHB40 and ZjNCED3 was negatively correlated with lateral main bud outgrowth in decapitated healthy jujube.Molecular evidence showed that ZjBRC1 interacted with ZjBRC2 via its N-terminus to activate ZjHB40 and ZjNCED3 expression and ABA accumulation in transgenic jujube calli.In addition,ZjBRC1 widely regulated differentially expressed genes related to ABA homeostasis and ABA signalling,especially by binding to and suppressing ABA receptors.Therefore,these results suggest that JWB phytoplasmas hijack the ZjBRC1-mediated ABA pathways to stimulate lateral bud outgrowth and expansion,providing a strategy to engineer plants resistant to JWB phytoplasma disease and regulate woody plant architecture to promote crop yield and quality.

On the measurements of individual particle properties via compression and crushing

An experimental study is presented to measure the elastic,yielding,and crushing properties of individual particles under compression using substrates made of aluminum alloy,stainless steel,and sapphire.Carefully selected,highly spherical individual Ottawa sand particles of 0.75e1.1 mm in nominal diameter were compressed between two smooth substrates,and the loadedeformation curves were analyzed by Hertz elastic contact theory to derive their reduced modulus and Young’s modulus as well as yielding and crushing strengths,which vary significantly with the type of substrate materials.Further analysis of the yielding and plastic deformation at the particle-substrate contact shows that the yield strength or hardness of the substrate materials dominates the local contact behavior and hence affects the measured apparent yielding and crushing strengths.The two softer substrates(aluminum alloy and stainless steel)actually lead to underestimated apparent shear yield strengths of quartz particles by 60.4%and 54.2%,respectively,which are actually the yielding of substrates,while the true particle yielding occurs in the sapphire-particle contact.Moreover,the two softer substrates cause much overestimated crushing strengths of the quartz particles by 50.4%and 36.4%,respectively.Selection of inappropriate substrate materials and inappropriate interpretation of the particle-substrate contact can lead to significant errors in the measured yielding and crushing strengths.It is recommended that single particle compression testing uses substrates with yield strength greater than that of the tested particles and result interpretation also considers the elastic and yielding behaviors of the substrates.

西双版纳户外运动进校园SWOT分析

本文以西双版纳户外运动进校园为研究内容,运用SWOT分析法分析了其优势(Strengths)、劣势(Weaknesses)、机会(Opportunities)、威胁(Threats),旨在对西双版纳户外运动进校园进行综合性分析,并提出相关建议。研究表明,西双版纳户外运动进校园的价值分别有:利于户外运动的推广和普及、丰富学校教育内容、培养学生综合能力、促进健康发展。户外运动进校园的优势在于;得天独厚的自然资源、多元民族文化优势、蓬勃发展的旅游业。其劣势在于:教育资源和专业指导不足、户外运动开展设施不足。其机会在于:国家政策与政府支持。其威胁在于:安全风险问题、学生与家长对户外运动认知不足、环境保护与可持续发展问题。