Institute of Crop Science (34h) Hormonl networks involved in phosphte deficiencyinduced cluster root formtion of Lupinus lus L. For PSP5 in Montpellier, 214 Zhengrui Wng, A.B.M. Moshiur Rhmn, Guoying Wng, Uwe Ludewig, Jino Shen, Günter Neumnn 27-August-214
Cluster roots (CRs) cluster roots my e regrded s the third mjor dpttion for nutrient (P) cquisition in higher plnts Cluster root morphology of Lupinus lus under P deficiency Rhizosphere cidifiction Skene, 1998, J. Ecol., 86: 162 Cluster root P moilizing function Well-investigted model for studies on root-induced P moilistion in the rhizosphere Citrte exudtion Ferric reductive cpcity Secretory cid phosphtse White lupin -P +Rock P +Pi -P Mize However, regultion of CR formtion is still poorly understood +Rock P +Pi Lmers et l., 213, Am. J. Bot., 1: 263 Bsed on Neumnn nd Mrtinoi, 22, Trends Plnt Sci., 7: 162; Neumnn nd Römheld, 22, Plnt roots: the hidden hlf, 617 2
The different stges of CR development MA Growth ctivity of lterl rootlets stops Meristem dies Dense covering with long root hirs Induction of cluster root ctivity Intense extrusion of protons, citrte, isoflvonoids nd cid phosphtse Intense Ferric reduction JU Outgrowth of lterl rootlets PE Formtion of cluster root primordi 5 cm Scle r : 1 cm PE: pre-emergent stge; JU: juvenile CR; MA: mture CR. 3
Hormonl control of CR formtion Comined pproch of: Trnscriptome sequencing (RNA-seq); Expression nlysis of hormone-relted genes; Hormone trnsport studies; Inhiitor studies; Physiologicl investigtions. 4
Auxin Diffusile IAA (ng per 2 shoots) 4 3 2 1 c CD A c AB BC cd cd D CD cd CD 8 1 12 14 16 18 2 22 Dys fter sowing -P (verge: 1.26) +P (verge: 1.26) 1 st CR No difference in shoot to root trnsloction of uxin in +P nd P plnts A c Reltive Gene Expression 2 1 -P_PE -P_JU -P_MA But: Intensive expression of genes relted with uxin iosynthesis nd trnsport in PE nd JU stges YUCCA AUX1 PIN1 c Auxin iosynthesis, redistriution (nd sensitivity) in the root tissue, rther thn shoot-derived uxin, my ply n essentil role for cluster root formtion 5
JU/PE MA/JU Ethylene RNA-seq dt: lue = significnt up-regultion, red = significnt down-regultion, white = no significnt chnge Reltive Gene Expression 4 3 2 1 RT-qPCR dt: -P_PE -P_JU -P_MA Low ethylene concentrtions stimulte lterl root growth ( low expression of ethylene iosynthesis genes in juvenile clusters) High ethylene concentrtions inhiit lterl root growth ( high expression in mture clusters) ACC_oxidse Fukki nd Tsk, 29, Plnt Mol. Biol., 69: 437 6
Ethylene -P control -P +CoCl 2 (1 μm) The ethylene ntgonist CoCl 2 completely locks CR formtion The first evidence tht ethylene is directly involved in cluster root formtion 7
Brssinosteroids (BRs) RNA-seq dt: lue = significnt up-regultion, red = significnt down-regultion, white = no significnt chnge JU/PE MA/JU Reltive Gene Expression 3 2 1 RT-qPCR dt: -P_PE -P_JU -P_MA BR Brssinosteroids cn stimulte lterl root growth y modulting uxin distriution nd cting s ethylene ntgonist Fukki nd Tsk, 29, Plnt Mol. Biol., 69: 437 Upregultion in PE nd JU clusters Downregultion in mture clusters where lterl rootlet elongtion stops 8
Brssinosteroids (BRs) CR primordi formed efore ppliction -P control -P Brz (3 μm) First evidence tht rssinosteroids re involved in cluster root formtion Scle: 1 cm The BR ntgonist rssinzole (Brz) completely inhiits CR formtion 9
Role of sucrose in CR formtion Scle: 5 cm +P -Suc -P -Suc +P +Suc (2.5 mm) Internl sucrose concentrtion in 2 cm - supicl root zones (PE) 1.8 mm.4 3.4 mm 1.1 P-limittion increses root concentrtion of sucrose Externl sucrose mimics CR formtion t physiologicl concentrtions 1
Sucrose cts s signl 5 4 Numer of CR 4 3 2 1 c Numer of CR 3 2 1 -P +P -P +P No sucrose Sucrose Sucrose (25 mm) induces CR formtion in +P plnts 5 +P control +P +Suc +P +Pl No CR formtion induced y Pltinose (sucrose nlogue, 25 mm) no osmotic effect 4 Numer of CR 3 2 1 No CR formtion induced y glucose + fructose (oth t 12.5 mm) no simple cron source effect Sucrose cts s signl +P control +P +Suc +P +Glu/Fru 11
Sucrose induces CR formtion vi interction with ethylene 4 Numer of CR per plnt 3 2 1 Control +CoCl2 Control +CoCl2 -P -Suc +P +Suc not detected The ethylene ntgonist CoCl 2 suppresses oth, P deficiency- nd sucrose-induced CR formtion 12
Are they functionl? Citrte exudtion (mg g -1 root FW) Reltive Gene Expression 9 6 3 8 6 4 2 Citrte exudtion LMATE -P +P -P +P No sucrose Sucrose PEPC ctivity (µmol NADHturn-over min -1 g -1 root FW) 1.8 1.2.6 1.2.6. Citrte synthesis c Sucrose c c induces CR formtion ut not CR ctivity. (root 1.8 exudtion) in +P plnts 6 Reltive Gene Expression LPEPC -P +P -P +P No sucrose c Sucrose Acid phosphtse ctivity (µmol PNP min -1 g -1 root DW ) Reltive Gene Expression Acid phosphtse ctivity 18 12 6 5 4 3 2 1 c LSAP -P +P -P +P No sucrose c Sucrose 13
Schemtic model of sucrose-hormone interctions in CR formtion SHOOT Incresed root-trnsloction of sucrose (pulses depending on source lef development) Low shoot P sttus ROOTS Externl sucrose supply Incresed sucrose concentrtion in roots Low root P sttus Incresed orgnic cid production citrte exudtion Secr. cid phosphtse low Incresed ethylene high Incresed uxin sensitivity Auxin trnsport Auxin synthesis Primordi formtion Promordi emergence Brssinosteroids CR mturtion P-retrnsloction Inhiition of elongtion Root hir prolifertion 14
Acknowledgement: A.B.M. Moshiur Rhmn, Guoying Wng, Uwe Ludewig, Jino Shen, Günter Neumnn Thnk you for your ttention!