Arabidopsis leucine-rich repeat malectin receptor-like kinases regulate pollen-stigma interactions.

Flowering plants contain tightly controlled pollen-pistil interactions required for promoting intraspecific fertilization and preventing interspecific hybridizations. In Arabidopsis (Arabidopsis thaliana), several receptor kinases (RKs) are known to regulate the later stages of intraspecific pollen tube growth and ovular reception in the pistil, but less is known about RK regulation of the earlier stages. The Arabidopsis RECEPTOR-LIKE KINASE IN FLOWERS1 (RKF1)/RKF1-LIKE (RKFL)1-3 cluster of four Leucine-Rich Repeat Malectin (LRR-MAL) RKs was previously found to function in the stigma to promote intraspecific pollen hydration. Here, we tested additional combinations of up to seven Arabidopsis LRR-MAL RK knockout mutants including RKF1, RKFL1-3, LysM RLK1-INTERACTING KINASE1, REMORIN-INTERACTING RECEPTOR1 and NEMATODE-INDUCED LRR-RLK2. These LRR-MAL RKs were discovered to function in the female stigma to support intraspecific Arabidopsis pollen tube growth and to establish a pre-zygotic interspecific barrier against Capsella rubella pollen. Thus, this study uncovered additional biological functions for this poorly understood group of RKs in regulating the early stages of Arabidopsis sexual reproduction.