The 30th International Conference on Arabidopsis Research (ICAR 2019)

490 / 2019-02-28 11:04:52

The receptor-like kinases BAM1 and BAM2 promote the cell-to-cell movement of miR165/6 in the root stele to regulate xylem patterning

miRNA movement,receptor-like kinase,TYLCV,xylem patterning,HD-ZIPIII

Plenary track > Development

Xylem patterning in the root is established through the creation of opposing gradients of miRNAs and their targets, enabled by the cell-to-cell movement of the former. More specifically, it has been reported that in the Arabidopsis root, miR165/6 move from the endodermis, where they are produced, inwards into the stele to regulate the expression of HD-ZIPIII family genes: upon establishment of this opposing gradient of miRNA and targets, xylem identity is determined. MiR165/6 move through plasmodesmata, but how their trafficking is regulated remains elusive. Here, we found that the simultaneous mutation of the receptor-like kinases BAM1 and BAM2 results in defects in xylem patterning. Bam1 bam2 double mutant plants display increased and less restricted mRNA accumulation of the HD-ZIP III miR165/6 targets in the root and lower accumulation of miR166 in the stele, although the total amount of miR165/6 is unaffected. Furthermore, transgenic Arabidopsis plants expressing the C4 protein from Tomato yellow leaf curl virus, which interacts with and inhibits BAM1 and BAM2, recapitulate the bam1 bam2 phenotype; this effect is non-cell-autonomous, since it can also be observed when C4 is expressed specifically in the endodermis. Therefore, we hypothesize that these phenotypes are due to impaired movement of miRNAs through BAM1 and BAM2, indicating a novel mechanism for the regulation of miRNA cell-to-cell movement and for a viral protein to manipulate host development.