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Department of Biological Sciences

The Krizek lab published a new study in Plant Molecular Biology

Flower development relies on a tight control of cell division and differentiation for the creation of floral organs of defined morphology and size. Floral meristems arise from the periphery of the dome-shaped inflorescence meristem during reproductive development and give rise to floral organ primordia in four concentric whorls. The four members of the AINTEGUMENTA-LIKE/PLETHORA (AIL/PLT) subfamily of AP2/ERF transcription factors AINTEGUMENTA (ANT), AIL5, AIL6, and AIL7 play important roles in floral organogenesis. ANT and AIL6 have partially overlapping roles in preventing premature differentiation of the floral meristem, regulating floral organ initiation and positioning, specifying organ identity, and promoting organ growth. In addition, loss of ANT function alone results in smaller floral organs and female sterility, indicating that some ANT functions cannot be compensated by AIL6. Differences in the functions of ANT and AIL6 appear to result primarily from differences in gene expression. ANT is expressed at much higher levels than AIL6 and in a broader domain that persists longer during floral organ development. Expression of AIL6 under the control of the ANT promoter largely complements an ant mutant, indicating that AIL6 can provide ANT function when expressed at the same levels and places as ANT. 

AIL5 and AIL7 make smaller contributions to floral organ development as compared with ANT and AIL6. Like AIL6, mutations in AIL5 or AIL7 have no phenotypic effect on their own but these mutations enhance ant single mutants. AIL5 has overlapping roles with ANT in sepal positioning and petal initiation and growth, while AIL7 has overlapping roles with ANT in sepal positioning, petal initiation, and carpel fusion. The different functions of ANT, AIL5, and AIL7 could result from differences in expression and/or from differences in protein activity. In their new study titled "Differences in both expression and protein activity contribute to the distinct functions of AINTEGUMENTA compared with AINTEGUMENTA-LIKE 5 and AINTEGUMENTA-LIKE 7", Dr. Beth Krizek and collaborators examined the ability of genomic copies of AIL5 and AIL7 to provide ANT function when expressed under the control of the ANT promoter. They found that only ANT:gAIL5 lines with much higher amounts of AIL5 mRNA as compared with ANT could compensate for loss of ANT function. ANT:gAIL7 lines with AIL7 mRNA levels similar to those of ANT were able to rescue some but not all aspects of the ant mutant phenotype. Altogether, these results indicate that differences in both expression and protein activity contribute to the functional specificity of ANT compared with AIL5 and AIL7.

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