|Monti, M. M.|
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2004
Publication Date: 8/1/2004
Citation: Guyon, V., Tang, W., Monti, M., Raiola, A., Lorenzo, G., McCormick, S., Taylor, L. 2004. Antisense phenotypes reveal a role for SHY, a pollen-specific leucine-rich repeat protein, in pollen tube growth. Plant Journal, 39(4):643-54. Interpretive Summary: SHY, a pollen-specific gene encodes a leucine-rich repeat protein. To test if SHY plays an important role during pollen germination, we expressed an antisense (AS) copy of the SHY cDNA in pollen. The tomato SHY interacts with a receptor kinase; this, and the AS-SHY phenotypes, suggest that SHY might function in mediating pollen tube growth.
Technical Abstract: Summary SHY, a pollen-specific gene identified in a screen for genes upregulated at pollen germination (Guyon et al., 2000), encodes a leucine-rich repeat (LRR) protein that is predicted to be secreted. To test if SHY plays an important role during pollen germination, we generated transgenic plants expressing an antisense (AS) copy of the SHY cDNA in pollen. Primary transformants exhibited poor seed set, but homozygous lines could be identified. In these lines, nearly all pollen tubes failed to reach the ovules; tube growth was arrested at the apex of the ovary and the pollen tubes exhibited abnormal callose deposits throughout the tube and in the tips. We show that a SHY::eGFP fusion protein is targeted to the cell wall. The structure of the SHY protein is nearly identical to other extracellular matrix glycoproteins that are composed of LRRs, such as the polygalacturonase inhibitor proteins (PGIP) of plants. PGIPs may function as defense proteins by inhibiting fungal endo-polygalacturonases, but enzyme assays with extracts of AS-SHY pollen do not support such an inhibitor role for SHY. The tomato ortholog of SHY interacts with a tomato receptor kinase (LePRK2) in yeast two-hybrid and pull-down assays (Tang et al., 2002, 2004); this, and the AS-SHY phenotypes, suggest instead that SHY might function in a signal transduction pathway mediating pollen tube growth