After double fertilization, zygotic activation occurs to initiate a new life cycle, followed by cell division, cell differentiation and organogenesis. During post-embryonic development, stem cells located in shoot apical meristem (SAM) and root apical meristem (RAM) allow plants to continuously generate new tissues and organs. Therefore, understanding the role of zygote activation and stem cell homeostasis has been of long-standing interest to scientists.

Recently, researchers led by Professor Liu Chunming from the Institute of Botany, Chinese Academy of Sciences (CAS), found that DEAD-box RNA helicase 27 (RH27) plays critical roles in miRNA biogenesis, zygote activation, and stem cell homeostasis.

The Arabidopsis genome has 58 genes encoding DEAD-box RNA helicases, some of which are implicated in RNA-related events including mRNA export, mRNA splicing and rRNA processing.

However, the role of DEAD-box RNA helicases in miRNA biogenesis has not been reported in plants. In this study, a zygote-lethal mutant zyg4-1 was identified, and map-based cloning showed that the mutation was caused by a point mutation in the RH27 gene.

RH27 regulates zygote division and stem cell homeostasis through miRNA biogenesis [IMAGE: KEY LABORATORY OF MOLECULAR PHYSIOLOGY, CHINESE ACADEMY OF SCIENCES]

Interestingly a weak allele of rh27-2 exhibited compromised stem cell homeostasis in both the SAM and RAM. In rh27-2 plants, the expression of stem cell homeostasis-related genes was up-regulated, alongside reduced levels of their regulatory miRNAs. Small RNA sequencing and RT-qPCR analyses showed reduced accumulations of a large subset of miRNAs and their pri-miRNAs in rh27-2.

Further biochemical studies revealed that RH27 is associated with pri-miRNAs in vivo and directly interacts with miRNA biogenesis components, DCL1, DDL, HYL1 and SE. These data together demonstrate that RH27 is a new component of the microprocessor complex, and is required for zygote division and stem cell homeostasis. This work indicates a potential role of miRNA in zygote activation and stem cell homeostasis.

This work was published online in The Plant Cell on November 17, 2020. It was performed by Liu Chunming’s group at the Institute of Botany, CAS, in collaboration with Professor Cao Xiaofeng’s group at the Institute of Genetics and Developmental Biology, CAS.

For more information, please contact:

Prof. Liu Chunming

Email:cmliu@ibcas.ac.cn; or

Associate Prof. Song Xiufen

E-mail: xfsong@ibcas.ac.cn

Institute of Botany, Chinese Academy of Sciences

Source: Key Laboratory of Plant Molecular Physiology,

Chinese Academy of Sciences