Maize LSC encoding a large subunit of ribonucleotide reductase is required for subsidiary cell development and plant growth.

Abstract

The four-celled stomatal complex consists of a pair of guard cells (GCs) and two subsidiary cells (SCs) in grasses, which benefits fast adjustment of stomatal pore aperture. The formation and development of SCs are thus important for stomatal functionality. Here, we report the maize loss of subsidiary cells (lsc) mutant with a large number of stomata lacking one or two SCs. The loss of SCs is supposed to be resulted from impeded subsidiary mother cells (SMC) polarization and asymmetrical division. Besides the defect in SCs, the lsc mutant also displays a dwarf morphology and pale and stripped newly-grown leaves. LSC encodes a large subunit of ribonucleotide reductase (RNR), an enzyme involved in deoxyribonucleotides (dNTPs) synthesis. Consistently, the dNTPs levels and expression of genes involved in DNA replication, cell cycle progression, and SC development were significantly reduced in the lsc mutant compared with the wild-type B73 inbred line. Conversely, overexpression of maize LSC increase dNTP synthesis and promotes plant growth in both maize and Arabidopsis. Our data indicate that LSC regulates dNTP production and is required for SMC polarization, SC differentiation, and plant growth.