The Kinase ERULUS Controls Pollen Tube Targeting and Growth in .

In this paper, we describe the role of the receptor-like kinase ERULUS (ERU) in PT growth of . analysis and transcriptional reporter lines revealed that is only expressed in pollen and root hairs (RHs), making it a tip growth-specific kinase. Deviations from Mendelian inheritance were observed in the offspring of self-pollinated heterozygous plants. We found that PT targeting was disturbed, providing a possible explanation for the observed decrease in fertilization competitiveness. Extracellular calcium perception and intracellular calcium dynamics lie at the basis of pollen tube (PT) tip growth and guidance. loss-of-function lines displayed no obvious PT phenotype, unless grown on low extracellular calcium ([Ca]) medium. When grown at 12 the normal [Ca], PTs grew 37% slower relative to WT PTs. Visualization of cytoplasmic [Ca] oscillations using the Yellow Cameleon 3.6 (YC3.6) calcium sensor showed that, unlike in WT PTs, apical [Ca] oscillations occur at a lower frequency when grown at lower [Ca], consistent with the observed reduced growth velocity. Our results show that the tip growth-specific kinase ERULUS is involved in regulating Ca-dependent PT growth, and most importantly, fertilization efficiency through successful PT targeting to the ovules.