Rice CASP1 regulates suberin deposition in small lateral roots and plays
crucial role in metal homeostasis in plant
Abstract
Arabidopsis Casparian strip membrane domain proteins (CASPs) form a
transmembrane scaffold to recruit lignin biosynthetic enzymes for
Casparian strip (CS) formation. Compared with Arabidopsis, rice root is
more complex with a CS of the exodermis and sclerenchyma and a CS that
does not block propidium iodide entry into the stele. Rice CASP1 is
highly similar to AtCASPs, but it is not required for CS formation. Its
mutation results in early leaf senescence and fewer tillers and does not
change the CS structure and permeability. OsCASP1 is mainly located in
the nuclear membrane. Its expression is concentrated in the root stele
and at small lateral root tips and can be induced by salt stress.
OsCASP1 mutation causes ectopic suberin deposition in small lateral
roots and ion imbalances in the plant. Homeostatic disorder induces
nutrient recycling and accelerate leaf senescence. To our knowledge,
OsCASP1 is the first CASP to be described in the nuclear membrane; it
modulates suberin deposition and does not involve CS formation,
representing a novel regulatory mode of CASPs.