Differentiation commitment is one of the most complex mechanisms to study in biological science. One of the model systems used for understanding differentiation complexity is heterocyst development in cyanobacteria. Cyanobacteria have the capability of biological nitrogen fixation due to highly differentiated heterocyst cells. Once the nitrogen deficiency signal is perceived by the cyanobacteria, few of its vegetative cells commit toward the development of heterocyst. Heterocyst provides a microoxic environment that is essential for the nitrogenase complex to fix the atmospheric dinitrogen. The entire process of development of heterocyst can be divided into different steps, such as (a) sensing signal and differentiation induction, (b) positional (pattern) determination of heterocyst in the filament, (c) formation of extracellular thick heterocyst‐specific layers, and (d) assembly of nitrogen‐fixing machinery. Many of the key regulators that are essential for heterocyst formation in these different steps have been identified. Recently, the role of small RNA and interruption DNA elements that influence the heterocyst formation and function has also been identified. In this review article, we have outlined the current understanding of the entire molecular circuit of heterocyst development in a simplistic way. This article focuses on explaining key concepts related to heterocyst development and discusses recent discoveries in this line.

中文翻译：

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蓝藻异囊分化的分子回路

分化承诺是生物科学中最复杂的研究机制之一。用于理解分化复杂性的模型系统之一是蓝藻中的异囊发育。由于高度分化的异囊细胞，蓝藻具有生物固氮能力。一旦蓝藻感知到缺氮信号，它的营养细胞就很少会发展成异型囊肿。杂囊提供了一个微氧环境，这对于固氮酶复合物固定大气二氮至关重要。杂囊发育的整个过程可以分为不同的步骤，例如（a）传感信号和分化诱导，（b）异囊在灯丝中的位置（模式）确定，(c) 细胞外厚杂囊特异性层的形成，以及 (d) 固氮机器的组装。已经确定了在这些不同步骤中对异囊形成必不可少的许多关键调节剂。最近，还确定了影响杂囊形成和功能的小 RNA 和中断 DNA 元件的作用。在这篇评论文章中，我们以一种简单的方式概述了目前对异囊发育的整个分子回路的理解。本文重点解释与异型囊发育相关的关键概念，并讨论这方面的最新发现。还确定了影响异囊形成和功能的小 RNA 和中断 DNA 元件的作用。在这篇评论文章中，我们以简单的方式概述了目前对异囊发育的整个分子回路的理解。本文重点解释与异型囊发育相关的关键概念，并讨论这方面的最新发现。还确定了影响异囊形成和功能的小 RNA 和中断 DNA 元件的作用。在这篇评论文章中，我们以一种简单的方式概述了目前对异囊发育的整个分子回路的理解。本文重点解释与异型囊发育相关的关键概念，并讨论这方面的最新发现。