Algae. 2009; 24(2): 85-91.
Epistatic Relationships of Two Regulatory Factors During Heterocyst Development
Young-Saeng Kim1, Il-Sup Kim1, Sun-Young Shin1, Hyun-Young Kim1, Sung-Ho Kang2 and Ho-Sung Yoon1*
1Department of Biology, Kyungpook National University, Daegu 702-701, Korea
2Division of Polar Biology & Ocean Sciences, Korea
Polar Research Institute (KOPRI), Get-Pearl Tower, Songdo Technopark 7-50, Songdo-Dong, Yeonsu-Gu, Incheon, 406-840, Korea
The filamentous cyanobacterium Anabaena sp. Strain PCC 7120 produces a developmental pattern of single heterocysts separated by approximately 10 vegetative cells. Heterocysts differentiate from vegetative cells and are specialized for nitrogen fixation. The patS gene, which encodes a small peptide that inhibits heterocyst differentiation, is expressed in proheterocysts and plays a critical role in establishing the heterocyst pattern. Another key regulator of heterocyst development is the hetR gene. hetR mutants fail to produce heterocysts and extra copies of hetR on a plasmid cause a multiple contiguous heterocyst phenotype. To elucidate the relationship between these two counter acting factors in the genetic regulatory pathway during heterocyst differentiation, the expression patterns of a patS-gfp and a hetR-gfp fusion were examined in a patS deletion and a hetR deletion strain. The results, in combination with the result from a hetR and patS double deletion strain, suggest patS and hetR are mutually antagonistic and the balance between these two factors in two different cell types (heterocysts and vegetative cells) may be critical during the decision making process on their cell fates.
Keywords : cellular differentiation, developmental genes, diffusible signal, epistatic relationship, mutual antagonistic