ABUNDANCE PATTERNS OF LILY POLLEN CDNAS - CHARACTERIZATION OF 3 POLLEN-PREFERENTIAL CDNA CLONES

Twenty-five clones were randomly selected from a mature pollen cDNA li brary of Easter lily (Lilium longiflorum Thunb.) in order to study the abundance of pollen-expressed mRNAs and the functional roles of the p roteins encoded by these mRNAs. Plaque hybridization experiments were conducted to estimate indirectly the expression level of the mRNAs. Ba sed on the hybridization frequency in the mature pollen library, the c DNA clones were divided into three abundance groups. Eight clones belo nged to a high abundance class in which each cDNA clone was present in the mature lily pollen library at a frequency between 0.3 and 3%. Six of these clones were not found in cDNA libraries made from carpel, le af, or root, suggesting that they are preferentially expressed in poll en. Fourteen clones belonged to a medium abundance class and were pres ent in the mature pollen library at a frequency between 0.01 and 0.08% . The remaining three clones, which were present at a frequency below 0.01%, were grouped as a low abundance class. Almost all of the cDNA c lones which belong to either the medium or low abundance class were al so detected in the leaf library. Northern blot hybridization with thre e of the highly abundant cDNA clones confirmed their preferential expr ession in anther. In situ hybridization experiment with one of the clo nes showed the pollen-specific expression of the clone in mature anthe r. DNA sequence analysis revealed that the clone LMP131 encodes a pept ide which is highly homologous to the tomato pollen-preferential gene, LAT59, which encodes a putative pectate lyase. The clone LMP134 encod es a peptide that shows an extensive similarity to a variety of thiore doxins. The third clone LMP132 encodes a 182-residue protein that has no significant homology to known sequences.