Transporter supplies manganese for cell wall biosynthesis.
Manganese is an important trace element for plants because, as a cation (Mn2+), it acts as a cofactor of various enzymes. These enzymes include glycosyltransferases localized in the Golgi, which synthesize the matrix polysaccharides for the plant cell wall. However, the supply of these enzymes with manganese is not well understood.
In their search for plant manganese transporters that ensure proper biosynthesis of cell wall components, scientists from the IPB and the University of Halle have recently characterized the candidate protein BIVALENT CATION TRANSPORTER 3 (BICAT3) from Arabidopsis in more detail. First, they showed that BICAT3 is specifically localized in the trans Golgi. When they expressed BICAT3 in yeast mutants with impaired transport of manganese (Mn2+) and calcium (Ca2+) ions, the missing yeast transporters could be complemented by the plant candidate protein - a first clear indication that BICAT3 can indeed transport Mn2+ ions. Moreover, Arabidopsis knockout mutants of BICAT3 were sensitive to low Mn2+ and high Ca2+ availability and showed altered intracellular Mn2+ distribution between the Golgi and chloroplasts. In bicat3 mutants, cell expansion and leaf size were also reduced compared with wild type. Also, the composition of matrix polysaccharides synthesized in the trans-Golgi was found to be disrupted under manganese-deficient conditions in bicat3 mutants. In addition to these vegetative growth defects, the scientists also observed an impairment in pollen tube growth of bicat3 plants, resulting in fewer seeds and shorter siliques.
In summary, the research team was able to show that BICAT3 is an important Mn2+ transporter in the trans-Golgi, which facilitates glycosylation reactions in the Golgi and ensures the intracellular distribution of Mn2+.
Original publication:
He J, Yang B, Hause G, Rössner N, Peiter-Volk T, Schattat MH, Voiniciuc C, Peiter E. The trans-Golgi-localized protein BICAT3 regulates manganese allocation and matrix polysaccharide biosynthesis. Plant Physiol. 2022 Aug 22:kiac387. doi: 10.1093/plphys/kiac387. Epub ahead of print.
