摘要
【目的】探究N-羰基辛酰基高丝氨酸内酯(AHL)家族成员3OC8-HSL对苹果耐盐性的调控作用,分析3OC8-HSL对实生苗生长、离子平衡及耐盐基因表达的影响,解析其分子调控机制,为果树抗盐砧木改良与栽培提供理论依据。【方法】以苹果常用砧木八棱海棠(Malus robusta)实生苗为研究对象,设置0 mmol·L^(-1)NaCl(正常生长条件)和200 mmol·L^(-1)NaCl(盐胁迫条件)两种处理,检测10μmol·L^(-1)的3OC8-HSL对植株生长、离子平衡、抗氧化能力及耐盐相关基因表达的影响。【结果】在正常生长条件下,3OC8-HSL处理显著促进八棱海棠实生苗生长,显著增加株高(+23.74%)、鲜质量(+17.23%)和叶绿素含量(+4.06%),表明3OC8-HSL对植物的生长具有促进作用。在盐胁迫条件下,3OC8-HSL处理增强了实生苗的耐盐性,显著增加株高(+11.61%)、鲜质量(+26.38%)和叶绿素含量(+36.98%),降低丙二醛(MDA)含量(-36.20%),降低Na^(+)含量(-11.01%)并提高K^(+)含量(+19.46%),由此显著降低了Na^(+)/K^(+)比值(-22.17%)。转录组分析表明,3OC8-HSL处理上调了多个耐盐相关通路基因的表达,主要涉及苯丙烷生物合成、谷胱甘肽代谢和木质素合成。【结论】3OC8-HSL可能通过调控生长发育、离子稳态、次生代谢物合成等通路,增强了八棱海棠实生苗的耐盐能力。
【Objective】The aim of this study was to investigate the effects of exogenous N-carbonyloctanoyl homoserine lactone(3OC8-HSL)on salt tolerance of Malus robusta seedlings by evaluating growth performance,physiological parameters,and the expression of salt-responsive genes under salt stress.【Methods】A greenhouse pot experiment was conducted with four treatment groups:Including the control group(CK,0 mmol·L^(-1)NaCl+water),the 3OC8-HSL treatment group(AC,0 mmol·L^(-1)NaCl+10μmol·L^(-1)3OC8-HSL),salt stress group(Salt,200 mmol·L^(-1)NaCl+water),and 3OC8-HSL+salt stress group(AS,200 mmol·L^(-1)NaCl+10μmol·L^(-1)3OC8-HSL).Each treatment was applied to the seedlings for 45 days.3OC8-HSL solution(10μmol·L^(-1))was drench-applied to the root zone on days 1,7,and 14,while salt stress was imposed by watering with 200 mmol·L^(-1)NaCl every 3 days.The growth parameters(plant height and fresh mass)were measured at the end of the experiment.The leaf chlorophyll content was determined(total chlorophyll,as well as chlorophyll a and b)as an indicator for photosynthetic status.The malondialdehyde(MDA)content in seedling roots was quantified to assess lipid peroxidation(oxidative stress damage).The leaf Na^(+)and K^(+)concentrations were measured,and the Na^(+)/K^(+)ratio was calculated to evaluate ionic homeostasis under each treatment.For molecular analysis,the root samples from salt-stressed seedlings with and without 3OC8-HSL were subjected to RNA sequencing(RNA-seq).Differentially expressed genes(DEGs)between the AS treatment and Salt treatment were identified using DESeq2(standard:|log2 fold change|>1 and adjusted p-value<0.05).The gene Ontology(GO)enrichment analysis was performed to characterize the biological processes enriched among these DEGs.Furthermore,four DEGs associated with stress responses were selected for validation by quantitative real-time PCR(RT-qPCR):MdPAL,MdGST,MdHKT1,and MdLRR-RLK.【Results】The Growth and Physiological Responses:Under non-saline conditions,the exogenous 3OC8-HSL markedly promoted the growth of Malus robusta seedlings.The treated seedlings exhibited a 23.74%increase in plant height and a 17.23%increase in fresh mass compared with the untreated controls,along with a slight but significant rise in the leaf chlorophyll content(+4.06%).These results indicated that 3OC8-HSL itself had a growth-promoting effect even without stress.Under salt stress(200 mmol·L^(-1)NaCl),3OC8-HSL application substantially improved seedling performance and stress tolerance.The 3OC8-HSL-treated salt-stressed seedlings grew taller(+11.61%plant height)and heavier(+26.38%fresh mass than those under salt stress alone.Notably,3OC8-HSL alleviated salt-induced damage:the treated seedlings maintained significantly higher chlorophyll levels(total chlorophyll+36.98%vs salt control),indicating better photosynthetic capacity under stress.In addition,3OC8-HSL reduced oxidative damage,as evidenced by a 36.20%reduction in root MDA accumulation under salt stress relative to untreated seedlings.This lower MDA level suggested that 3OC8-HSL would enhance the antioxidant defense,thereby protecting cellular membranes from peroxidation damage caused by salt stress.The Ion Homeostasis:3OC8-HSL also improved ionic balance in Malus robusta under salinity.In the salt-stressed seedlings,3OC8-HSL treatment led to significantly lower Na^(+)accumulation and higher K^(+)retention in plant tissues.Specifically,the Na^(+)content in the 3OC8-HSL-treated seedlings was 11.01%lower than that in the untreated salt-stressed controls,while the K^(+)content was 19.46%higher.Consequently,The Na^(+)/K^(+)ratio,a key indicator of ion homeostasis under salt stress,was reduced by 22.17%in the 3OC8-HSL group compared with the salt treatment alone.This improvement in Na^(+)/K^(+)homeostasis reflected a better maintenance of ionic equilibrium,which is crucial for salt tolerance.The results suggested that 3OC8-HSL would help seedlings limit sodium uptake or transport and/or enhance potassium uptake,thereby mitigating ion toxicity under high salinity.Consistently,the treated seedlings showed healthier morphology and less salt injury than the untreated ones(greener leaves,less wilting),as observed qualitatively during the experiment.The Gene Expression and Pathway Activation:The transcriptome profiling of roots under salt stress revealed significant molecular changes due to 3OC8-HSL.A total of 560 genes were differentially expressed in the 3OC8-HSL-treated vs.untreated salt-stressed roots,with 177 genes upregulated and 383 downregulated(adjusted P<0.05).The GO enrichment analysis of these DEGs indicated that 3OC8-HSL activated multiple stress-responsive pathways.Many of the upregulated genes were associated with secondary metabolite biosynthesis and defense-related processes.In particular,biological process categories such as phenylpropanoid biosynthetic and metabolic pathways(involved in the synthesis of lignin and other phenolics),glutathione metabolism,response to wounding,and cuticle development were significantly enriched among the 3OC8-HSL-induced genes.These results implied that 3OC8-HSL would trigger a broad reprogramming of the plant’s stress response at the molecular level,enhancing both structural and chemical defenses under the salt stress.Importantly,several key salt-tolerance genes were strongly upregulated by 3OC8-HSL treatment.For instance,transcripts of the MdPAL(phenylalanine ammonia-lyase,a rate-limiting enzyme in the phenylpropanoid pathway leading to lignin synthesis)increased 4.6-fold in the 3OC8-HSL-treated roots(after 7 days of salt stress)compared with the untreated controls.The MdHKT1,encoding a high-affinity K^(+)transporter involved in Na^(+)/K^(+)homeostasis,was upregulated 9.6-fold,and the MdLRRRLK,encoding a leucine-rich repeat receptor-like kinase implicated in stress signal perception,rose by 8.4-fold(both after 7 days).Additionally,the MdGST(glutathione S-transferase,involved in detoxification and ROS scavenging via the glutathione pathway)showed a 6.4-fold induction at 24 hours after treatment.The robust induction of these genes,which would play roles in lignin biosynthesis(cell wall fortification),antioxidant activity,ionic transport,and stress signaling,would underscore the multi-faceted mechanism by which 3OC8-HSL would enhance salt tolerance.【Conclusion】This study demonstrated that the exogenous 3OC8-HSL improved the salt tolerance of Malus robusta seedlings by promoting growth,enhancing photosynthetic capacity,maintaining Na^(+)/K^(+)homeostasis,and reducing oxidative damage.The transcriptome and RT-qPCR analysis showed that the 3OC8-HSL upregulated the expression of the MdPAL,MdGST,MdHKT1,and MdLRR-RLK,and activated pathways related to phenylpropanoid metabolism and glutathione metabolism under the salt stress.These results would provide a theoretical basis for the application of AHL signals in improving salt resistance of apple rootstocks.
作者
刘东鑫
李红飞
邓立乐
潘莹安
金强
张锐
潘志勇
LIU Dongxin;LI Hongfei;DENG Lile;PAN Ying’an;JIN Qiang;ZHANG Rui;PAN Zhiyong(College of Horticulture and Forestry,Tarim University,Alar 843300,Xinjiang,China;College of Horticulture and Forestry,Huazhong Agricultural University,Wuhan 430070,Hubei,China)
出处
《果树学报》
北大核心
2026年第2期270-278,共9页
Journal of Fruit Science
