Abstract
In Arabidopsis (Arabidopsis thaliana), jasmonate is a key signal required for stamen and pollen maturation and thus for male fertility. Using transcriptional profiling, we have previously identified a set of 13 transcription factors that are proposed to be involved in controlling jasmonate responses in stamens. This finding suggests that a transcriptional cascade regulates the many developmental and biochemical pathways required to ensure fertility; however, the organization of this cascade is currently not understood. Here, we provide a genetic characterization of the role of MYB108 and map its relationship to MYB21 and MYB24, two other transcription factors involved in the jasmonate response in Arabidopsis stamens. Transcriptional profiling and analysis of plants expressing a MYB108:GUS fusion protein demonstrated that MYB108 expression is largely confined to sporophytic tissues of the stamen. Three allelic myb108 mutants exhibited reduced male fertility that was associated with delayed anther dehiscence, reduced pollen viability, and decreased fecundity relative to wild type. These phenotypes were all found to be exacerbated in myb108 myb24 double mutants, which also had shorter stamen filaments. Measurements of MYB108 transcript levels in wild-type and mutant flowers showed that expression of this gene is strongly dependent on MYB21. Taken together, our results indicate that MYB108 and MYB24 have overlapping functions and act downstream of MYB21 in a transcriptional cascade that mediates stamen and pollen maturation in response to jasmonate.
Highlights
In Arabidopsis (Arabidopsis thaliana), jasmonate is a key signal required for stamen and pollen maturation and for male fertility
Seed was collected from one homozygous plant of each line and designated myb108-1 (SALK_056061), myb108-2 (SALK_024059), and myb108-3 (CSHL_GT6213). myb108-1 and myb108-2 are in the Columbia (Col-0) background, while myb108-3 is derived from the Landsberg erecta (Ler) ecotype
Our previous transcript profiling experiments showed that jasmonate initiates a transcriptional cascade in Arabidopsis stamens that is required for stamen maturation and male fertility (Mandaokar et al, 2003, 2006)
Summary
In Arabidopsis (Arabidopsis thaliana), jasmonate is a key signal required for stamen and pollen maturation and for male fertility. In Arabidopsis, jasmonate signaling is required for fertility, and mutants that are deficient in jasmonate synthesis (McConn and Browse, 1996; Sanders et al, 2000; Stintzi and Browse, 2000; Ishiguro et al, 2001; Park et al, 2002) or in jasmonate signaling (Feys et al, 1994; Chini et al, 2007; Thines et al, 2007) are male-sterile These mutants show a characteristic set of developmental defects. When flower clusters were treated with a single application of jasmonate, only flower buds that were in the middle of stage 12 at the time of application produced seed; buds at earlier or later stages of development remained sterile (Stintzi and Browse, 2000) These observations suggest that jasmonate triggers developmental programs required for stamen and pollen maturation
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