玉米果穗顶部籽秕粒瘪或未结籽粒，称之为秃顶，又叫“秃尖”，是玉米生产中常见的现象，一般会导致玉米减产5%～10%，严重的甚至在30%以上。造成玉米秃尖有品种的遗传因素，但也受到种植密度和干旱胁迫等环境条件的影响。近日，为了解析玉米秃尖的分子生理机制，阿根廷布宜诺斯艾利斯大学的科研人员系统研究了杂交品种、播种密度和灌溉条件对玉米秃尖的影响。进一步地，研究人员在同步人工授粉后的2-6天内，收集果穗籽粒样本研究其基因表达模式并分析籽粒的糖份含量。研究发现具有高败育风险的籽粒中葡萄糖和果糖含量增加，而FASCICLIN-LIKE阿拉伯半乳聚糖蛋白基因(FLA)的表达与籽粒败育呈负相关，且ZmFLA7基因的表达只在果穗的顶部响应干旱胁迫。在干旱胁迫和β-GlucosylYariv的药剂处理条件下，籽粒中的阿拉伯半乳聚糖蛋白(AGP)含量降低，进而加剧了籽粒的败育。类似地，干旱胁迫也减少了拟南芥角果中AtFLA9基因的表达。拟南芥FLA9基因缺失突变体的功能分析表明，AtFLA9基因表达调控也与籽粒败育呈负相关。基于基因表达模式，药理学和遗传学证据，该研究结果表明环境胁迫诱导FLA基因的下调表达是玉米和拟南芥籽粒败育的主要原因。

Plant,Cell&Environment,5January2018

ReducedexpressionofselectedFASCICLIN-LIKEARABINOGALACTANPROTEINgenesassociateswiththeabortionofkernelsinfieldcropsofZeamays(maize)andofArabidopsisseeds

Authors

JuanIgnacioCagnola,GonzaloJavierDumontdeChassart,SilviaElizabethIbarra,...MaríaElenaOtegui,JoséManuelEstevez,JorgeJoséCasal

UniversidaddeBuenosAires,Argentina

Abstract

Abortionoffertilisedovariesatthetipoftheearcangeneratesignificantyieldlossesinmaizecrops.Toinvestigatethemechanismsinvolvedinthisprocess,twomaizehybridsweregrowninfieldcropsattwosowingdensitiesandunderthreeirrigationregimes(wellwateredcontrol,droughtbeforepollinationanddroughtduringpollination),inallpossiblecombinations.Samplesofeartipsweretaken2-6daysaftersynchronoushandpollinationandusedfortheanalysisofgeneexpressionandsugars.Glucoseandfructoselevelsincreasedinkernelswithhighabortionrisk.SeveralFASCICLIN-LIKEARABINOGALACTANPROTEIN(FLA)genes,showednegativecorrelationwithabortion.TheexpressionofZmFLA7respondedtodroughtonlyatthetipoftheear.Theabundanceofarabinogalactanprotein(AGP)glycanepitopesdecreasedwithdroughtandpharmacologicaltreatmentsthatreduceAGPactivityenhancedtheabortionoffertilisedovaries.DroughtalsoreducedtheexpressionofAthFLA9inthesiliquesofArabidopsisthaliana.Gain-andloss-of-functionmutantsofArabidopsisshowedanegativecorrelationbetweenAthFLA9andseedabortion.Basedongeneexpressionpatterns,pharmacologicalandgeneticevidence,weproposethatstress-inducedreductionsintheexpressionofselectedFLAgenesenhanceabortionoffertilisedovariesinmaizeandArabidopsis.