cDNA array analysis of stress‐induced gene expression in barley androgenesis

Abstract

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 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.

Buthionine sulfoximine (BSO)-mediated improvement in cultured embryo quality in vitro entails changes in ascorbate metabolism, meristem development and embryo maturation

“…In animal systems GSTs are expressed especially during embryonic and fetal growth where they support normal growth and development by reducing the levels of toxic organic hydroperoxides (Raijmakers et al 2001). A similar role may also be exercised during plant embryo development, as this ubiquitous group of proteins has been shown to increase during embryo development in a variety of culture systems (Vrinten et al 1999;Galland et al 2001;Maraschin et al 2006). BSO-mediated up-regulation of several GSTs may therefore be required for protecting the developing embryos against stress conditions, thereby ensuring successful growth and normal development.…”

Identification of proteins related to microspore embryogenesis responsiveness in anther cultures of winter triticale (×Triticosecale Wittm.)

“…First genes identified during induction of ME in barley encoded a lipid transfer protein-ECLTP, a glutathione-S-transferase-ECGST and arabinogalactan-like protein-ECA1 (Vrinten et al 1999), but further analysis revealed that only ECA1 was expressed specifically in embryogenic cells. In barley, Maraschin et al (2006), using microarrays containing ESTs (expressed sequence tags) identified a very distinct gene expression profile characteristic for embryogenic microspores. In comparison with developing pollen, in embryogenic microspores upregulation of genes involved in protein degradation (ubiquitin-conjugating enzyme, 20S proteasome subunit alpha-5 and alpha-2, 26S protease subunit-8, cysteine and aspartic protease and FtsH metalloprotease), starch and sugar hydrolysis (maltase, cell wall invertase), stress response (GTS, catalase), metabolism (alcohol dehydrogenase 3) and cell signalling (GTPase) was detected.…”

Expression Profiles in Barley Microspore Embryogenesis

“…Thus, YABBY5, ZML2, CURLY LEAF and ICE1 could play a direct role in microspore reprogramming. Previously in barley, Maraschin et al (2006) revealed that genes encoding an alcohol dehydrogenase 3 (ADH3), and proteolytic genes as a metalloprotease FtsH, a cysteine protease precursor, an aspartic protease, and a 26S proteasome regulatory subunit, could represent bio-markers for the embryogenic potential of microspores. These results indicated that metabolic changes and proteolysis have a critical role in the dedifferentiation phase of microspore embryogenesis.…”

“…Among these stress-response genes, genes encoding glutathione S-transferases (GSTs) were overrepresented, representing a total of 2% of the up-regulated genes. GSTs are involved in oxidative stress response, pathogen attack and heavy metal toxicity (Marrs 1996) and the induction of members of the GST family during the initial steps of microspore embryogenesis has been described (Vrinten et al 1999;Maraschin et al 2006). With regard to heat shock proteins (HSPs), which have been reported to be highly expressed in microspores of rapeseed and tobacco upon heat shock and starvation (Cordewener et al 1995;Zarsky et al 1995;Smykal and Pechan 2000), only minor changes in the expression of the HSP genes were observed in this study.…”

“…In recent years, the availability of large sets of expressed sequence tags (ESTs) have triggered the development of macro-and microarray technology approaches that provide a rich source of information of the molecular processes that take place during microspore embryogenesis, specially at the microspore reprogramming phase (Maraschin et al 2006;Muñoz-Amatriaín et al 2006).…”