microRNA 166: an evolutionarily conserved stress biomarker in land plants targeting HD-ZIP family

Abstract

MicroRNAs (miRNAs) are significant class of noncoding RNAs having analytical investigating and modulatory roles in various signaling mechanisms in plants related to growth, development and environmental stress. Conserved miRNAs are an affirmation of land plants evolution and adaptation. They are a proof of indispensable roles of endogenous gene modulators that mediate plant survival on land. Out of such conserved miRNA families, is one core miRNA known as miR166 that is highly conserved among land plants. This particular miRNA is known to primarily target HD ZIP-III transcription factors. miR166 has roles in various developmental processes, as well as regulatory roles against biotic and abiotic stresses in major crop plants. Major developmental roles indirectly modulated by miR166 include shoot apical meristem and vascular differentiation, leaf and root development. In terms of abiotic stress, it has decisive regulatory roles under drought, salinity, and temperature along with biotic stress management. miR166 and its target genes are also known for their beneficial synergy with microorganisms in leguminous crops in relation to lateral roots and nodule development. Hence it is important to study the roles of miR166 in different crop plants to understand its defensive roles against environmental stresses and improve plant productivity by reprogramming several gene functions at molecular levels. This review is hence a summary of different regulatory roles of miR166 with its target HD-ZIP III and its modulatory and fine tuning against different environmental stresses in various plants.

Conservation and Diversity of miR166 Family Members From Highbush Blueberry (Vaccinium corymbosum) and Their Potential Functions in Abiotic Stress

“…Thus, miR166 family members are highly conserved across diverse plant species, especially along the 3′ arm ( Barik et al, 2014 ). Mature miR166 members are known to regulate the abundance of transcripts encoding HD-ZIP III transcription factors in many species ( Boualem et al, 2008 ; Li R. et al, 2018 ; Yadav et al, 2021 ). In this study, we predicted that all Vco-miR166s derived from the 3′ arm target HD-ZIP III transcripts, supporting the functional conservation of miR166 family members in various species ( Supplementary Table S6 ).…”

“…In plants, miR166 is a highly conserved miRNA implicated in a wide range of cellular and physiological processes by regulating its cognate target genes encoding members from the homeodomain leucine zipper (HD-ZIP III) family of transcription factors ( Miyashima et al, 2013 ; Singh et al, 2014 ; Yadav et al, 2021 ). Recent evidence showed that the miR166 family plays crucial roles in response to abiotic stress.…”

microRNAs and Their Roles in Plant Development

“…Mutations in miRNA transcription or processing complexes usually have multiple effects on plant from and function, indicating that miRNAs are important to coordinate plant development. For example, the roles of HD-ZIP III-miR165/166 pathway are important in the development of vascular, meristem, and leaf polarity, and the roles of miR156/ miR172 are important in flowering time and flower pattern (D' Ario et al, 2017;Ramachandran et al, 2017;Du et al, 2020;Ma et al, 2020;Lian et al, 2021;Yadav et al, 2021). During plant development, endogenous miRNAs play an important role in gene regulation by targeting related target genes.…”

Deep origin and gradual evolution of transporting tissues: Perspectives from across the land plants

“…However, these are accompanied by pleiotropic defects in gametophore development ( Yip et al, 2016 ), which makes inference of a role in conductive tissue development difficult. HD-ZIP III genes are regulated by the deeply conserved miRNA165/166 ( Tsuzuki et al, 2016 ; Yip et al, 2016 ; Yadav et al, 2021 ), and this suggests that a miRNA/HD-ZIP III module may broadly operate in controlling transporting tissue development.…”