Isolation of pollen early genes and analysis of expression pattern during the development of male gametophyte

The early events of pollen development are critical for the differentiation of male gametophyte. However, little is known about the molecular events that are unique to the early stages of pollen development. This study of gene expression during the pollen development is focused on identifying the early genes in Nicotiana tabacum anthers and characterizing the expression and regulation of these genes. A subtraction cDNA library was prepared from the early stages of pollen development (from dyad till uninucleate stage) and 113 unique genes differentially expressed were identified. Searches of the Nicotiana and other non-redundant database disclosed known or likely functions for 73 genes while 40 genes were of unknown function. Among those with unknown function 24 found matches in EST database while 16 showed 'no hit' or were novel. Northern blot analysis of 16 randomly picked clones as probes confirmed their expression in early stages of pollen development and no expression or lower expression in later stages. The tissue-specific expression studies showed that among these, 12 genes are anther-specific. To the best of our knowledge, these groups of clones represent the largest collection of 'early genes' isolated so far.