Authors: Houman Fei Ruichuan Zhang Richard P Pharis Vipen K Sawhney
Publish Date: 2004/04/24
Volume: 219, Issue: 4, Pages: 649-660
Abstract
Earlier we reported that mutation in the Male Sterile33 MS33 locus in Arabidopsis thaliana causes inhibition of stamen filament growth and a defect in the maturation of pollen grains Fei and Sawhney 1999 Physiol Plant 105165–170 Fei and Sawhney 2001 Can J Bot 79118–129 Here we report that the ms33 mutant has other pleiotropic effects including aberrant growth of all floral organs and a delay in seed germination and in flowering time These defects could be partially or completely restored by low temperature or by exogenous gibberellin A4 GA4 which in all cases was more effective than GA3 Analysis of endogenous GAs showed that in wild type WT mature flowers GA4 was the major GA and that relative to WT the ms33 flowers had low levels of the growth active GAs GA1 and GA4 and very reduced levels of GA9 GA24 and GA15 precursors of GA4 This suggests that mutation in the MS33 gene may suppress the GA biosynthetic pathway that leads to GA4 via GA9 and the early 13H C20 GAs WT flowers also possessed a much higher level of indole3acetic acid IAA and a lower level of abscisic acid ABA relative to ms33 flowers Low temperature induced partial restoration of male fertility in the ms33 flowers and this was associated with partial increase in GA4 In contrast in WT flowers GA1 and GA4 were very much reduced by low temperature Low temperature also had little effect on IAA or ABA levels of ms33 flowers but did reduce 2fold IAA levels in WT flowers The double mutants ms33 aba11 an ABAdeficient mutant and ms33 spy3 a GA signal transduction mutant had flower phenotypes similar to ms33 Together the data suggest that the developmental defects in the ms33 mutant are unrelated to ABA levels but may be causally associated with reduced levels of IAA GA1 and GA4 compared to WT flowersThe Authors thank Dr B Mulligan of University of Nottingham UK for kindly providing the ms33 seed and Dr LN Mander of the Australian National University for deuterated GAs H Fei acknowledges the support of a University of Saskatchewan Graduate scholarship during the course of this work This research was supported by NSERC of Canada Discovery grants to VKS and RPP
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