Developmental and Structural Section
Hirsch, Ann M. , De Hoff, P.L. , Deng, Weimin , Lee, Angie .
An open-flower mutant of Melilotus alba Desr., white sweetclover.
Melilotus alba Desr., white sweetclover, is an alternative papilionoid legume host for Sinorhizobium meliloti, a model nitrogen-fixing bacterium. In an attempt to find a floral mutant that might be more amenable to flower dip transformation, we uncovered an open-flower mutant, designated opf, in a genetic screen looking for nodulation responses of fast neutron bombardment mutants. Although the mutant developed normal nodules, the opf mutants developed flowers with reflexed bracts, sepals, and petals such that the stamens and carpels were exerted in contrast to wild-type sweetclover flowers. Based on crosses to the wild-type, we determined that the mutant segregated as a single, Mendelian recessive. However, crosses could be performed only when the opf mutant served as the female, suggesting that the mutant was male sterile. This led us to determine if there were developmental defects. Structural evaluations of early stage anther and pollen formation indicated no obvious difference from wild-type flowers. However, mature anthers did not dehisce, and rare pollen escapes from cracks in the anther wall were released as a sticky mass rather than as single grains. Two types of male sterility mutants showing varying degrees of anther indehiscence have been described for Arabidopsis: mutants where the stamens do not completely elongate, and those where the stamens elongate normally. The former are the result of defects in the jasmonic acid (JA) signaling pathway, whereas the latter are a result of mutations in genes encoding transcription factors. The opf mutant stamens have normally elongated filaments suggesting that they are more similar to the second class where the filaments elongate to wild-type length, the endothecium expands, but the pollen is not released (1, 2).
(1) Mitsuda N et al. (2005) Plant Cell 17:2993.
(2) Steiner-Lange S et al. (2003) Plant J 34:519.
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1 - UCLA, Department of MCD Biology and Molecular Biology Institute, 405 Hilgard Avenue, Los Angeles, CA, 90095-1606, USA
2 - University of California-Los Angeles, Dept. of Molecular, Cell and Developmental Biology
3 - University of California-Los Angeles, Plant Growth Center
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Maybird/Cliff Lodge - Level C
Date: Tuesday, July 28th, 2009
Time: 4:15 PM