Plastid genome structure and plastid-related transcript levels in albino barley plants derived from anther culture

Abstract

Southern analysis of DNA from four albino barley plants regenerated from microspores by direct embryogenesis revealed the presence of plastid genomes which had undergone deletion or alteration of specific restriction fragments (delta ptDNAs). In contrast, a fifth plant appeared to contain an intact plastid genome. All the albino plants studied contained reduced amounts of ptDNA, the most abundant restriction fragments being present at levels between 6% and 20% of those found in the leaves of green seedlings. Steady-state levels of transcripts from plastid and nuclear genes encoding plastid components were estimated by Northern analysis of RNA from albino plants. Transcripts from the plastid genes rbcL, psbD-psbC and the 16S and 23S rRNAs were undetectable or were present at greatly reduced levels in albino plants compared to those found in green leaves. Transcripts from the nuclear genes rbcS and cab, which encode chloroplast localised proteins, were also present at reduced levels in albino pollen plants. Levels of the nuclear encoded 25S rRNA, which is not a plastid component, were found to be identical in albino plants and green leaves suggesting that only the expression of plastid-related genes may be affected in albino plants. The general reduction of plastid-related transcripts was independent of the different patterns of ptDNA alteration seen in albino pollen plants.

Identification of QTLs associated with albino plant formation and some new facts concerning green versus albino ratio determinants in triticale (×Triticosecale Wittm.) anther culture

“…Although, large defects in the ptDNA structure are often detected among albino plants regenerated, it cannot be treated as the primary cause of albinism. Changes were also identified in the transcription levels of the nucleuscoded chloroplast-localized proteins (Dunford and Walden 1991) what indicates the important role of the nuclear genome in proper plastid function. Based on crosses between albinism-susceptible and albinismresistant cultivars, it has been concluded that the genes responsible for this character are inherited in a Mendelian fashion and hence, they must be nuclear encoded (Larsen et al 1991).…”

“…Albino plants showed an aberrant form of plastids and, frequently, deletions in their plastid DNA (Harada et al 1991;Hofinger et al 2000). It was proved that transcript levels of plastid encoded genes for photosynthetic proteins and ribosomal RNA were generally heavily reduced in albino plants in relation to green plants (Ankele et al 2005;Dunford and Walden 1991;Hofinger et al 2000). Translation deficiencies and the modified transcript pattern in androgenic albino plants could be explained by lack of functional plastid ribosomes (Hofinger et al 2000).…”

Differential development of plastids during microspore embryogenesis in barley

“…During microspore embryogenesis, deletions in plastid DNA were detected, involving rRNA synthesis and protein transcription (Dunford andWalden 1991, Mouritzen andHolm 1994). The nuclear genome of albino plantlets is also affected, especially genes encoding for some plastid-targetted proteins (Dunford andWalden 1991, Larsen et al 1991).…”

“…Androgenetic albino plantlets were investigated in order to understand the origin of albinism and undifferentiated plastids with a few thylakoids and starch were found in both microspore-derived embryos and albino plantlets (Mlodzianowski andIdzikowska 1981, Sunderland andHuang 1985). During microspore embryogenesis, deletions in plastid DNA were detected, involving rRNA synthesis and protein transcription (Dunford andWalden 1991, Mouritzen andHolm 1994). The nuclear genome of albino plantlets is also affected, especially genes encoding for some plastid-targetted proteins (Dunford andWalden 1991, Larsen et al 1991).…”

Effect of Cold Pretreatment, Anthers Orientation, Spikelet Position and Donor Tiller on the Callusing Response in Barley Anther In vitro Culture

“…The negative effect of this cold pretreatment was clearly represented in the quality of regenerating, there were more albinos plantlets regenerated in the cold pre-treated series. This is probably due to alterations that can reach the plastid DNA as the deletion or amendment of certain sequences [36,38], but also the prevention of differentiation of plastids chloroplasts under the conditions of culture [26].…”