Hierarchical Action of Mulberry miR156 in the Vegetative Phase Transition

Abstract

The vegetative phase transition is a prerequisite for flowering in angiosperm plants. Mulberry miR156 has been confirmed to be a crucial factor in the vegetative phase transition in Arabidopsis thaliana. The over-expression of miR156 in transgenic Populus × canadensis dramatically prolongs the juvenile phase. Here, we find that the expression of mno-miR156 decreases with age in all tissues in mulberry, which led us to study the hierarchical action of miR156 in mulberry. Utilizing degradome sequencing and dual-luciferase reporter assays, nine MnSPLs were shown to be directly regulated by miR156. The results of yeast one-hybrid and dual-luciferase reporter assays also revealed that six MnSPLs could recognize the promoter sequences of mno-miR172 and activate its expression. Our results demonstrate that mno-miR156 performs its role by repressing MnSPL/mno-miR172 pathway expression in mulberry. This work uncovered a miR156/SPLs/miR172 regulation pathway in the development of mulberry and fills a gap in our knowledge about the molecular mechanism of vegetative phase transition in perennial woody plants.

The Mulberry SPL Gene Family and the Response of MnSPL7 to Silkworm Herbivory through Activating the Transcription of MnTT2L2 in the Catechin Biosynthesis Pathway

“…In mulberry, the TT2L1 and TT2L2 proteins interact with bHLH3 or GL3 to promote proanthocyanidin (the multimer of catechin or epicatechin) accumulation [40]. Furthermore, mulberry genome sequencing has been completed [33,41], and our previous study also verified that nine mulberry SPL genes are directly regulated by miR156 [42]. However, to date, systematic research on mulberry SPL genes is still lacking; consequently, the specific molecular biological functions of SBP-box transcription factor genes in development and stress responses remain unclear.…”

“…These results suggest that plant SPL genes may have originated from common ancestral genes, but some SPL genes may have been differentiated separately between monocots and eudicots. Nine MnSPL genes have been verified as the target genes of miR156 in mulberry [42]. Here, we found that most of the miR156-target MnSPLs clustered with miR156-target AtSPLs, except for MnSPL7 and MnSPL14 (Figure 2).…”

Identification and Functional Prediction of CircRNAs in Leaves of F1 Hybrid Poplars with Different Growth Potential and Their Parents

“…For example, miR398 and its target partner superoxide dismutase1 (CSD1) are involved in the regulation of abscisic acid (ABA) and salt stress related pathways of poplar and Arabidopsis thaliana [53]; PtmiR169o can enhance the drought resistance of poplar by inhibiting the expression of its target gene PtNF-YA6, thereby promoting its growth [39]. In addition, we also found that a large number of circRNAs target miRNA family members that play a key role in plant organ development, growth phase transition, and phenological regulation, such as the miR156 and miR157 families [38,40,[54][55][56]. miRNA156/157 combines with the miRNA recognition element (MRE) of the SPL3 gene of Arabidopsis thaliana to promote early flowering [38].…”

“…Among the different types of miRNA, more members of the miR156, miR157, and miR169 families were targeted (Table S17). Some members of these families have been confirmed to affect the plant stress response, organ development, growth phase transformation, and phenological regulation by regulating the expression of their target genes [38][39][40]. miR5021, miR156, miR5641, miR5649, and miR5998 were all targeted by a large number of circRNAs (Table S17).…”

“…miRNA156/157 combines with the miRNA recognition element (MRE) of the SPL3 gene of Arabidopsis thaliana to promote early flowering [38]. The expression of miR156 in poplar decreases with age, and the juvenile stage of transgenic plants overexpressing miR156 was significantly prolonged [40]. It is worth noting that a large number of members of these miRNA families have targeted binding relationships with circRNA.…”