Two classes of pollen-specific, heat-stable proteins in Lilium longiflorum

Several floral organ-specific proteins in lily anthers do not accumulate to detectable levels until just before anthesis. Antisera were raised against three of these proteins. designated LLA, in pollen of Lilium longiflorum Thunb. cv. Snow Queen. Monospecific antibodies were further prepared from antisera to investigate the specificity and distribution of these proteins during development. In an effort to study the function of these gene products, pollen protein was heat-treated at 90°C for 10 min. Monospecific anti-LLA-32 and -23 antibodies recognized two of these heat-stable proteins with molecular masses of 32 and 23 kDa. Accumulation of the two proteins in anther development was correlated with desiccation that occurred naturally in the pollen. Immunob-lot analyses of total protein from floral and vegetative organs confirmed that both LLA-32 and -23 proteins were pollen-specific. The proteins showed consistent patterns of expression during development and their levels decreased when pollen germinated. The properties of the two proteins differed in responsiveness to both polyethylene glycol 8000 and abscisic acid, and in solubility characteristics. Analysis of amino acid composition indicates that both LLA-32 and -23 proteins are rich in glutamic acid/glutamine and glycine, a characteristic of heat-stable proteins. However, LLA-23 has more polar amino acid residues with a polarity of 57%, two-fold higher than that of the LLA-32. Immunoblot analyses showed that LLA-32 and -23 proteins were immunologically unrelated to the dehydrin-like protein in lily seeds. It concluded that the two classes of pollen-specific proteins have some features in common with each other and with dehydrins. but that each is distinct.