Epistatic Relationships of Two Regulatory Factors During Heterocyst Development

doi:2009.24.2.85

Algae > Volume 24(2); 2009 > Article

Algae 2009;24(2): 85-91. doi: https://doi.org/10.4490/algae.2009.24.2.085

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

*Corresponding Author

Email: hyoon@knu.ac.kr

ABSTRACT

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.

Key words: cellular differentiation, developmental genes, diffusible signal, epistatic relationship, mutual antagonistic