缺铁胁迫对杜梨幼苗生理及铁吸收和转运相关基因表达的影响

Effects of iron deficiency stress on physiology and gene expression of iron absorption and transpotation in Pyrus betulaefolia

[目的]本文旨在探讨缺铁胁迫下杜梨幼苗铁素吸收与转运相关生理生化特性和相关基因时空表达的差异,为解决梨树生产中极易产生的缺铁黄化问题提供理论依据。[方法]以杜梨幼苗为试材,采用全根及分根水培法,设置正常供铁(40μmol·L^(-1) FeNa-EDTA,简写为+Fe)及缺铁(0μmol·L^(-1) FeNa-EDTA,简写为-Fe)、分根供铁(1/2根供40μmol·L^(-1) FeNa-EDTA、1/2根供0μmol·L^(-1) FeNa-EDTA,简写为+Fe SR和-Fe SR)处理,研究铁素对杜梨幼苗的根系形态、质外体铁、有机酸含量等及相关基因表达的影响。[结果]处理12 d时,-Fe、+Fe SR和-Fe SR处理的总根长分别是相应处理0 d的1.76、3.02和3.20倍;不同铁处理根际pH值随时间的上升趋势均比+Fe处理缓慢;Fe^(3+)还原酶活性随不同铁处理时间先增强后下降;缺铁处理下根和叶中有机酸含量始终高于正常供铁处理。缺铁处理下铁吸收和转运相关基因表达显著上调,并随时间呈不同的变化规律,其中根系IRT1、FRO2、HA7基因2 d即显著上调表达,NRAMP1在中、后期(6 d)显著上调表达;CS1、CS2和NAS1在根系和叶片均表达,而NAS2和FRD3仅在根系表达;YSL3仅在叶中表达,且在8 d时显著上调表达。[结论]缺铁胁迫显著改变杜梨的根系形态,根系铁吸收相关的基因表达加强,根系还原能力提高;同时,调控有机酸类物质合成和转运的基因也上调表达,有利于促进铁螯合物由根系向地上部转运。

[Objectives]The experiment investigated the physiological and molecular responses of Pyrus betulaefolia rootstock under iron deficiency stress,aiming to provide theoretical basis for solving the problem of iron deficiency chlorosis which is common in pear production.[Methods]The study was carried out by using P.betulaefolia rootstock as materials with three treatments:normal iron treatment(40μmol·L^-1 Fe,+Fe),iron deficiency(0μmol·L^-1 Fe,-Fe)and split-root conditions(1/2 root for 40μmol·L^-1 Fe,1/2 root for 0μmol·L^-1 Fe,abbreviated as+Fe SR and-Fe SR)in split-root and whole-root hydroponic system.The root growth indexes,content of apoplast iron,citric acid and malice acid and RT-qPCR analysis of some key genes in Fe^2+uptake and transport including IRT 1,FRO2,HA7,NRAMP1,NRAMP3,FRD3,CS1,CS2,NAS1,NAS2,YSL3 were detected.[Results]At 12 days after transplanting,the total root length of-Fe,+Fe SR and-Fe SR treatments were 1.76,3.02 and 3.20 times that of 0 d respectively.Compared with+Fe treatment,the rhizosphere pH increased slowly and Fe 3+reductase activity increased firstly and then decreased.The contents of organic acids in roots and leaves under Fe deficiency were always higher than those in+Fe.Under Fe deficiency treatment,the expression of genes related to Fe absorption and transport of P.betulaefolia increased significantly and showed different changes with time.Among them,the expression of IRT 1,FRO 2 and HA 7 were significantly up-regulated in 2 d under-Fe treatment,and NRAMP 1 was up-regulated in mid and late stage(6 d)of-Fe treatment.Moreover,the expression of genes involved in the synthesis and transport of organic acids was up-regulated,e.g.CS 1,CS 2 and NAS 1 mainly expressed in roots and leaves.However,NAS 2 and FRD 3 only expressed in the roots,YSL 3 gene only expressed in the leaves and was strongly up-regulated on the 8th day.[Conclusions]Iron deficiency will promote the morphological changes of P.betulaefolia.Important genes related to iron absorption is up-expressed in roots.The ability of root proton pump to enhance H+secretion and the activity of Fe 3+reductase activity increase root reduction ability.Simultaneously,genes which regulate the synthesis and transport of organic acids are up-regulation expression,promoting the formation of chelates with iron transport to shoots.