ccd7 - 6th International Symposium on Root Development

Strigolactones t inhibit adventitious rootformation in cuttingsMandy RasmussenUniversiteit Gent

Adventitious Root FormationHormone SignalsAuxin generallypromotes rootsCytokinin inhibitsadventitious i roots

Inconsistent trends between root formation andauxinIAA (ng /g fw)300200100numberof advent titious root ts16120 0wt mutant1 rms4 mutant2 rms284WT mutant1 rms4 mutant2 rms2LowstrigolactoneNormalstrigolactonePlant Physiol. (1994) 104: 953‐959Plant Physiol. (1996) 110: 859‐865

Q: How does strigolactone affectadventitious root formation?

Adventitious Root FormationHormone SignalsAuxin generallypromotes rootsGomez‐Roldan et al (2008) Nature455:189‐194Umehara et al (2008) Nature 455:195‐200Cytokinin inhibitsadventitious i rootsStrigolactones ???

Strigolactone SignallingCarotenoidprecursorstrigolactonesCCD7FboxCCD8ProductionResponseBudBranchingoutgrowth• Carotenoid derivedU d i• Upwards movingsignal• Promote mycorrhyzae& parasitic weed seedgermination

Strigolactones inhibit the number of adventitious rootsNumbe r of advent titious roo ts20ControlStrigolactone151050abcc c Pea resultsaWild WT type production ccd8 reception FboxmutantCCD7CCD8ProductionstrigolactonesFboxResponseAdventitiousBudrootoutgrowthoutgrowth

Strigolactones inhibit the number of adventitious rootsNum mber of ad dventitiousroots76543210aWild Type0 nM strigolactone1000 nM strigolactonecfb d bemax1 <strong>ccd7</strong> ccd8production mutantstcol max1 max3 max4 max2eggFboxCCD7CCD8ProductionstrigolactonesFboxResponseAdventitiousrootoutgrowth

Model TestingCCD7CCD8strigolactonesFboxAdventitiousrootoutgrowthStrigolactone mutants also have low xylem cytokininWTccd8<strong>ccd7</strong>Production mutantsCould this cause the increasedadventitious rooting?Morris et al. (2001) Plant Physiology126:1205‐1213

Model Testingstrigolactones1CCD7FboxCCD8AdventitiousrootoutgrowthXylemCytokinins2strigolactonesti tCCD7FboxCCD8CytokininAdventitiousrootoutgrowth

Cytokinins and strigolactones act independently to inhibitadventitious rootsNumb ber of adve entitious roots98765432100 nM strigolactone100 nM strigolactoneceadbbentitious rootsNumb ber of adv0 nM Cytokinin50 nM Cytokinin987654321eecadb bdb b0Col ipt1,5,7 ahk3,4 WTcol max1productionmax3 max4 max2CytokininproductionmutantCytokininreceptionmutantmutantsfresponsemutant

Model Testing1strigolactonesCCD7FboxCCD8AdventitiousrootoutgrowthXylemCytokinins2strigolactonesCCD7FboxCCD8CytokininAdventitiousrootoutgrowth

Model TestingAuxinCCD7CCD8strigolactonesFboxAdventitiousrootoutgrowthXylemCytokinins

Auxin does not control Strigolactone production;Strigolactone does not control auxin productionNumbe er of adve entitious roots432100 IAA10-7 IBA10-71dbb 0,75c cawild type production mutantr of adve entitious rootsNumbe0,5025 0,250controlstrigolactone caabWT yucca-D

ModelAuxinCCD7CCD8strigolactonesFboxAdventitiousrootoutgrowthXylemCytokininsAuxin promotes adventitious rooting even in strigolactonedeficient mutants

Adventitious Root FormationHormone SignalsAuxin movesbasipetallyRoot derivedCK is removedRoot derivedstrigolactonesremoved

Adventitious Root FormationHormone SignalsAuxin movesbasipetallyRoot derived CKbegins again =inhibits rootinitiationiti Adventitiousroot primordiainitiateAuxin increasesStrigolactonest= inhibits rootinitiation

Summary1. Strigolactones inhibit adventitious root formation in two species2. Cytokinin and strigolactone control adventitious rootingindependently3 Strigolactone and auxin act independently at different times to3. Strigolactone and auxin act independently at different times tocontrol adventitious rooting.

Rasmussen and Hunt (2010) Aus. For. 73 (1): 41‐46The Problem

Possible rooting promotersous rootsNumber ofadventiti40c3020100baWT control WT fluridone Production mutantCCD7CCD8ProductionstrigolactonesInhibit strigolactone production with fluridone(carotenoid inhibitor)Fboxresponserootoutgrowth

Possible rooting promotersadventitio ous roots432aPlumbagoababbNumber of10RH 0 4 20 100 500Fluridone concentration ti (nM)CCD7CCD8ProductionstrigolactonesInhibit strigolactone production with fluridone(carotenoid inhibitor)Fboxresponserootoutgrowth

StrigolactoneNewly found part ofadventitious root formationPotential solution forcutting propagation

Thanks:Christine Beveridge and labChrista Ci CritchleyMike MasonSanti KrisantiniDanny Geelen (UGent)Marie Curie<strong>International</strong> IncomingFellowshipsCollaboratorsCatherine Rameau (INRA Versailles, France)Catherine Bellini (UPSC, Sweden)Carmen Diaz‐Sala (Universidad de Alcala de Henares)Giel van Noorden (University of Gent, VIB)Tom Beeckman (University of Gent, VIB)Sofie Gormachtig (University of Gent, VIB)Carolien De Cuyper (University of Gent, VIB)QLD Agrisciences, DEEDISteven UnderhillMark HuntTim SmithStephen Trueman Forests NSWGeoff PeggMichael HensonLesley FrancisHelen SmithChris MoranDepartment of Employment, EconomicDevelopment and Innovation (DEEDI)Funding Queensland <strong>International</strong> FellowshipUQ Graduate School Research Travel Grant