Control of plasma membrane-associated actin polymerization specifies the pattern of the cell wall in xylem vessels.
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ABSTRACT: Cell wall patterning is central to determining the shape and function of plant cells. Protoxylem and metaxylem vessel cells deposit banded and pitted cell walls, respectively, which enable their distinctive water transport capabilities, but the mechanisms that specify which cell wall pattern is laid down remain unknown. Here, we show that the pitted cell wall pattern in metaxylem vessels is specified by transcriptional control of actin polymerization. A newly isolated allele of KNOTTED-like homeobox transcription factor 7 (KNAT7) was associated with the formation of banded cell walls in metaxylem vessels. To identify the genes responsible for altering the cell wall pattern in knat7 xylem vessels, we performed an RNA-seq analysis of knat7. We used in vitro cultures of hypocotyls and cotyledons because the population of differentiating xylem cells in intact roots is tiny and these methods efficiently induce ectopic differentiation of xylem vessel elements. Formin Homology Domain-Containing Protein 11 (FH11) was upregulated in knat7 metaxylem, but expressed only in protoxylem vessels in wild-type plants. Loss of FH11 suppressed the knat7 phenotype. Conversely, ectopic overexpression of FH11 in metaxylems mimicked the knat7 phenotype. FH11 function required its plasma membrane anchoring and the actin polymerization activity. Actin polymerization by FH11 at the plasma membrane caused the dispersion of activated ROP GTPases, the determinant of pit formation. These results suggest that decontrol of actin polymerization at the plasma membrane abolishes the pitted cell wall formation and promotes the formation of banded cell walls in metaxylem vessels. This study unveils the importance of the proper control of actin polymerization on cell wall pattern specification.
ORGANISM(S): Arabidopsis thaliana
PROVIDER: GSE286145 | GEO | 2025/01/15
REPOSITORIES: GEO
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