Tubby-like Protein 2 regulates homogalacturonan biosynthesis in Arabidopsis seed coat mucilage
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A possible transcription factor TLP2 was identified to be involved in the regulation of HG biosynthesis in Arabidopsis seed mucilage. TLP2 can translocate into nucleus from plasma membrane by interacting with NF-YC3. The discovery of TLP2 gene function can further fulfill the regulatory network of pectin biosynthesis in Arabidopsis thaliana.
Arabidopsis seed coat mucilage is an excellent model system to study the biosynthesis, function and regulation of pectin. Rhamnogalacturonan I (RG-I) and homogalacturonan (HG) are the major polysaccharides constituent of the Arabidopsis seed coat mucilage. Here, we identified a Tubby-like gene, Tubby-like protein 2 (TLP2), which was up-regulated in developing siliques when mucilage began to be produced. Ruthenium red (RR) staining of the seeds showed defective mucilage of tlp2-1 mutant after vigorous shaking compared to wild type (WT). Monosaccharide composition analysis revealed that the amount of total sugars and galacturonic acid (GalA) decreased significantly in the adherent mucilage (AM) of tlp2-1 mutant. Immunolabelling and dot immunoblotting analysis showed that unesterified HG decreased in the tlp2-1 mutant. Furthermore, TLP2 can translocate into nucleus by interacting with Nuclear Factor Y subunit C3 (NF-YC3) to function as a transcription factor. RNA-sequence and transactivation assays revealed that TLP2 could activate UDP-glucose 4-epimerase 1 (UGE1). In all, it is concluded that TLP2 could regulate the biosynthesis of HG possibly through the positive activation of UGE1.
KeywordsTLP2 Transcription factor Nucleus translocation Homogalacturonan Galacturonic acid
This work was supported by the National Natural Science Foundation of China (31470291, 31670302), the National Key Technology R&D Program (2015BAD15B03), the Taishan Scholar Program of Shandong (to GZ) and the Elite Youth Program of Chinese Academy of Agricultural Sciences (to YK).
MW, ZX, YK, RH and GZ conceived the study. MW, ZX and YW performed the experiments. MW analyzed the data and ZX prepared the figures. MW, ZX, Ahmed. RI and YK drafted the manuscript. All of the authors discussed the results, edited the manuscript, and approved the final manuscript.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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