Abstract
Transcription factors (TFs) and transcriptional regulators are important switches in transcriptional networks. In recent years, the transcriptional regulator TIE1 (TCP interactor containing EAR motif protein 1) was identified as a nuclear transcriptional repressor which regulates leaf development and controls branch development. However, the function and regulatory network of GhTIE1 has not been studied in cotton. Here, we demonstrated that GhTIE1 is functionally conserved in controlling shoot branching in cotton and Arabidopsis. Overexpression of GhTIE1 in Arabidopsis leads to higher bud vigor and more branches, while silencing GhTIE1 in cotton reduced bud activity and increased branching inhibition. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that GhTIE1 directly interacted with subclass II TCPs (GhBRC1, GhBRC2, and GhTCP13) in vivo and in vitro. Overexpression of GhBRC1, GhBRC2, and GhTCP13 in mutant brc1-2 partially rescued the mutant phenotype and decreased the number of branches, showing that these TCPs are functionally redundant in controlling branching. A transient dual-luciferase reporter assay indicated that GhTIE1 repressed the protein activity of GhBRC1 and GhTCP13, and thereby decreased the expression of their target gene GhHB21. Gene expression level analysis in GhTIE1-overexpressed and silenced plants also proved that GhTIE1 regulated shoot branching via repressing the activity of BRC1, HB21, HB40, and HB53. Our data reveals that shoot branching can be controlled via modulation of the activity of the TIE1 and TCP proteins and provides a theoretical basis for cultivating cotton varieties with ideal plant types.
Highlights
Branch development plays a decisive role in controlling aboveground plants, and the aboveground parts of crops are closely related to growth and yield (Kebrom et al, 2012)
Despite the low similarity of TIE1 between Arabidopsis and cotton, some of the conserved domains of the two GhTIE1s are highly similar to AtTIE1: the N-terminal region contains a helical region, and the C-terminal region contains a typical EAR motif sequence (DLELRL), showing that GhTIE1a and GhTIE1d may possess a similar function to AtTIE1 as a transcriptional repressor (Figure 1A) (Yang et al, 2018)
GhTIE1-YFP was infiltrated into tobacco leaves to detect transient expression, and the results showed that GhTIE1a and GhTIE1d proteins were localized in the nucleus and the cytoplasm, but this was more pronounced in the nucleus (Figures 1B, C)
Summary
Branch development plays a decisive role in controlling aboveground plants, and the aboveground parts of crops are closely related to growth and yield (Kebrom et al, 2012). The development of shoots begins with axillary meristem and develops into small shoots (McSteen and Leyser, 2005; Pasternak et al, 2019; Wang et al, 2019). The regulatory network consists of plant hormones and transcription factors (TFs) that can break the dormancy of small shoots and eventually develop into lateral branches (Rameau et al, 2015; Wang and Jiao, 2018). GhTIE1 in Controlling Plant Branching complex branching pattern consisting of fruit branches, vegetative shoots, and axillary buds. Developing and cultivating the ideal plant type affects cotton production and saves a lot of labor. The study of cotton branching control provides an important theoretical basis for improvement of cotton plants
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