Role for Arabidopsis in Stomatal Movement, Seed Mucilage Attachment, and Leaf Serration.

Phospholipase C (PLC) has been suggested to play important roles in plant stress and development. To increase our understanding of PLC signaling in plants, we have started to analyze knock-out (KO), knock-down (KD) and overexpression mutants of , which contains nine PLCs. Earlier, we characterized and . Here, the role of is functionally addressed. Promoter-GUS analyses revealed that is specifically expressed in the phloem of roots, leaves and flowers, and is also present in trichomes and hydathodes. Two T-DNA insertion mutants were obtained, i.e., being a KO- and a KD line. In contrast to earlier characterized phloem-expressed mutants, i.e., and , no defects in primary- or lateral root development were found for mutants. Like mutants, they were less sensitive to ABA during stomatal closure. Double-knockout lines were lethal, but double mutants were viable, and revealed several new phenotypes, not observed earlier in the single mutants. These include a defect in seed mucilage, enhanced leaf serration, and an increased tolerance to drought. Overexpression of enhanced drought tolerance too, similar to what was earlier found for -and overexpression. P-labeling of seedlings and treatment with sorbitol to mimic drought stress, revealed stronger PIP responses in both drought-tolerant and - mutants. Together, these results show novel functions for PLC in plant stress and development. Potential molecular mechanisms are discussed.