A stress-inducible protein associated with desiccation in lily pollen

Abstract

This work characterizes a stress-inducible protein (LLA) associated with desiccation in lily (Lilium longiflorum Thunb. cv Snow Queen) pollen. Immunoblots of two-dimensional polyacrylamide gels of pollen protein indicated that the LLA-32 protein with a molecular mass of 32 kDa was heterogeneous and had an isoelectric point of 5.6. The protein was developmentally regulated at the later stage of pollen maturation during anther development. The accumulation of LLA-32 proteins remained steady in the mature pollen, but the protein disappeared during pollen germination. Subcellular fractionation of pollen proteins revealed that the protein was detected only in the cytoplasmic fraction, indicative of a gametophytic origin. Premature drying of developing pollen demonstrated that the LLA-32 doublet was associated with desiccation. The accumulation of the proteins can be experimentally manipulated by methyl jasmonate and salicylic acid as well as by mannitol and methyl viologen. Differential accumulation of the doubler polypeptides occurred with response to various stimuli. The upper band of LLA-32 doubler polypeptides markedly accumulated upon dehydration whereas the lower band of LLA-32 doublet significantly increased its level of accumulation when other stresses were applied.