Poster: Plant Pathogen/Symbiont Interactions

Abs # 739: Lem2: a Novel Jacalin-Related, Lemma- and Palea-Specific Gene of Barley

Presenter:	Abebe, Tilahun , tabebe@wisc.edu
Authors	Abebe, Tilahun  (A)   Skadsen, Ron  (B)   Kaeppler, Heidi  (A)
Affiliations:	(A): Department of Agronomy, University of Wisconsin-Madison (B): usda/ars/ccru

The lemma and palea are photosynthetically active organs that supply developing kernels with carbon and nitrogen. Because of their rigid structure, the lemma and palea can also protect the kernel from pathogens and herbivory. Very little is known about the types of genes expressed in order for the lemma and palea carry out their functions. Using the suppression subtractive hybridization (SSH) method, we have identified many genes preferentially expressed in the lemma/palea, compared with the flag leaf. Among these we have characterized in detail a novel jacaline-like gene, Lem2. Lem2 is a multigene family with up to four copies in the barley genome. Restriction digestion of BACs containing large genomic DNA inserts indicated that all the Lem2 genes are located in a single chromosomal region. Using an F2 population of barley varieties, Lem2 was mapped to chromosome 5(1H) Bin 02 (near the short arm telomere; Kleinhoffs et. al.). Interestingly, Lem2 hybridizes with a single band only from Morex but not in Steptoe, Harrington, and Q21861. Northern analysis showed that Lem2 is specifically expressed in the lemma, palea and coleoptile. These organs have one common function, i.e. protection of internal organs. The LEM2 protein contains two jacalin-like domains. The jacalin domain is present in 1 to 6 copies in lectins and is involved in pathogen recognition. Furthermore, SA and MeJA treatment of spikes induces Lem2 expression in 2-4 hours. These results suggest that Lem2 is a defense-related gene. LEM2 may bind pathogens by its jacaline-like lectin domains. We have cloned the promoter of Lem2 and evaluated its ability to drive reporter gene expression. Transient studies showed strong expression of gfp in the lemma and palea with very weak expression in the leaf.