Post-embryonic function of GLOBULAR EMBRYO 4 (GLE4)/ OsMPK6 in rice development

In plants, mitogen activated protein kinases (MPKs) are involved in various signaling pathways that lead to biotic and abiotic responses as well as that regulate developmental processes. Among them, MPK6 and its closely related homologue, MPK3, act redundantly and are known to be involved in asymmetric cell divisions of meristemoid mother cells in stomata development and of zygotes in Arabidopsis. Loss-of-function mutants of GLE4/OsMPK6, which is an orthologue of MPK6 in rice, showed a defect in polarity establishment in early stage of embryogenesis. However, because of the embryo lethality of the mutations, the function of GLE4/OsMPK6 in post-embryonic development is not clarified. Here, we report the analysis of post embryonic function of GLE4/OsMPK6 in vegetative stage of rice using regenerated gle4/osmpk6 homozygous plants from tissue culture. The regenerated plants are dwarf and produce multiple shoots with small leaves. These shoots never develop into reproductive stage, instead, proliferate vegetative shoots repeatedly. Leaves of gle4/osmpk6 have small leaf blade at the tip and blade-sheath boundary become obscure. Stomata arrangement is also disturbed in gle4/osmpk6 leaf blade. The shape of shoot apical meristem of gle4/osmpk6 become disorganized. Thus, GLE4/OsMPK6 functions in shoot organization and stomata patterning in the post embryonic development in rice.