Minisymposium 15: Pollen Biology

Abs # M1502: The novel intracellular LRR proteins PIRL1 and PIRL9 are required for Arabidopsis pollen development and viability

Presenter:	Vernon, Daniel M       Contact Presenter
Authors	Forsthoefel, Nancy R (A)   Dao, Thuy P (A)   Geiser, Heidi A (A)   Vernon, Daniel M (A)
Affiliations:	(A): Department of Biology and Program in Biochemistry, Biophysics & Molecular Biology, Whitman College
Web Site:	http://people.whitman.edu/%7Evernondm

PIRLs (Plant Intracellular Ras-group-related LRRs) are a plant-specific family of leucine-rich repeat proteins structurally related to a class of animal and fungal LRR proteins that interact with Ras GTPases and serve as scaffold components in signal transduction complexes. We have carried out a systematic reverse-genetic study of the Arabidopsis PIRL family and initiated 2-hybrid screens to identify PIRL-interacting proteins. Here we describe results for the closely-related PIRL1 and PIRL9 genes. Pirl1 and pirl9 T-DNA knockout alleles were identified. Single mutant alleles displayed normal Mendelian inheritance and homozygotes did not exhibit obvious developmental defects. To investigate possible functional redundancy, we attempted to construct pirl1;pirl9 double mutants. However, double mutant progeny could not be recovered, suggesting lethality and/or transmission failure of the double-mutant allele combination. PCR genotyping of progeny produced by reciprocal crosses between wild type and pirl1;pirl9 carriers demonstrated that the mutant allele combination is transmitted normally through the female gametophyte, but is not transmitted via pollen. Scanning electron microscopy of pollen produced by pirl1-/-;pirl9+/- and pirl1-/+,pirl9-/- individuals revealed that ~50% of the pollen was severely malformed, consistent with the expected segregation of the double-mutant allele combination. Alexanders staining indicated that malformed pollen is not viable. Thus, PIRL1 and PIRL9 likely take part in intracellular signaling, transport, or regulatory processes essential for pollen development. 2-hybrid screens with a PIRL1 bait construct identified prospective PIRL interacting proteins, including some with potential signaling functions. Progress with further binding and specificity assays will be reported. -- Supported by USDA award 2002350412304 to D.M.V.; microscopy and imaging equipment supported by a grant from the WM Keck Foundation