Different aspects of androgenesis induction have been studied in detail, but little is known about the molecular mechanisms associated with this developmental switch. We have employed macroarrays... Show moreDifferent aspects of androgenesis induction have been studied in detail, but little is known about the molecular mechanisms associated with this developmental switch. We have employed macroarrays containing 1421 expressed sequence tags covering the early stages of barley zygotic embryogenesis to compare the gene expression profiles of stress-induced androgenic microspores with those of uninucleate microspores as they progressed into binucleate stage during pollen development. Principal component analysis defined distinct sets of gene expression profiles that were associated with androgenesis induction and pollen development. During pollen development, uninucleate microspores were characterized by the expression of cell division-related genes and transcripts involved in lipid biosynthesis. Progress into binucleate stage resulted in the significant increase in the level of transcripts associated with starch biosynthesis and energy production. These transcripts were downregulated in androgenic microspores. These results indicate that stress blocks the expression of pollen-related genes. The induction of androgenesis by stress was marked by the upregulation of transcripts involved in sugar and starch hydrolysis, proteolysis, stress response, inhibition of programmed cell death, and signaling. Further expression analysis revealed that the induction of genes encoding alcohol dehydrogenase 3, metalloprotease FtsH, cysteine protease 1 precursor, phytepsin precursor (aspartic protease), and a 26S proteasome regulatory subunit was associated with the androgenic potential of microspores, whereas the induction of transcripts involved in signaling and cytoprotection was associated with stress responses. Taken together, these expression profiles represent ‘bio-markers’ associated with the androgenic switch in microspores, providing a substantial contribution toward understanding the molecular events underlying stress-induced androgenesis. Show less
