Identification of a Mg-protoporphyrin IX monomethyl ester cyclase homologue, EaZIP, differentially expressed in variegated Epipremnum aureum ‘Golden Pothos’ is achieved through a unique method of comparative study using tissue regenerated plants

Abstract

Variegated plants provide a valuable tool for studying chloroplast biogenesis by allowing direct comparison between green and white/yellow sectors within the same leaf. While variegated plants are abundant in nature, the mechanism of leaf variegation remains largely unknown. Current studies are limited to a few mutants in model plant species, and are complicated by the potential for cross-contamination during dissection of leaf tissue into contrasting sectors. To overcome these obstacles, an alternative approach was explored using tissue-culture techniques to regenerate plantlets from unique sectors. Stable green and pale yellow plants were developed from a naturally variegated Epipremnum aureum 'Golden Pothos'. By comparing the gene expression between green and pale yellow plants using suppression subtractive hybridization in conjunction with homologous sequence search, nine down-regulated and 18 up-regulated genes were identified in pale yellow plants. Transcript abundance for EaZIP (Epipremnum aureum leucine zipper), a nuclear gene homologue of tobacco NTZIP and Arabidopsis CHL27, was reduced more than 4000-fold in qRT-PCR analysis. EaZIP encodes the Mg-protoporphyrin IX monomethyl ester cyclase, one of the key enzymes in the chlorophyll biosynthesis pathway. Examination of EaZIP expression in naturally variegated 'Golden Pothos' confirmed that EaZIP transcript levels were correlated with leaf chlorophyll contents, suggesting that this gene plays a major role in the loss of chlorophyll in the pale yellow sectors of E. aureum 'Golden Pothos'. This study further suggests that tissue-culture regeneration of plantlets from different coloured sectors of variegated leaves can be used to investigate the underlying mechanisms of variegation.

Accumulation of high OPDA level correlates with reduced ROS and elevated GSH benefiting white cell survival in variegated leaves

“…The PGs regenerated from green leaf sectors of ‘Golden Pothos’27 were included as a control. The VPG and PG had low levels of OPDA, but VPY had 4.4-fold higher OPDA than VPG (Fig.…”

Transcriptome profiling characterizes phosphate deficiency effects on carbohydrate metabolism in rice leaves

“…Chlorophyll is essential for photosynthesis and is linked to photosynthetic ATP production. The conversion of chlorophyllide ˛ to chlorophyll depends on uroporphyrinogen decarboxylase (Mock and Grimm, 1997), Mg chelatase (Jung et al, 2003a), Mg protoporphyrin IX methyltransferase (Pontier et al, 2007), Mg-protoporphyrin IX monomethyl ester cyclase (Bang et al, 2008;Hung et al, 2010), and 3,8-divinyl(proto) chlorophyll(ide) a 8-vinyl reductase (Wang et al, 2010). However, the chlorophyll content was not significantly changed by the activity of protoporphyrinogen oxidase in rice (Jung et al, 2003b).…”

Differential expression of a novel gene EaF82a in green and yellow sectors of variegated Epipremnum aureum leaves is related to uneven distribution of auxin

“…In a variegated leaf, the green sectors contain normal chloroplasts while the color defective sectors contain undifferentiated plastids or dysfunctional chloroplasts (Wetzel et al , Sakamoto , Yu et al ). In addition, cells in the color defective sectors are viable (Kato et al , Hung et al ) and do not appear to interfere with proper chloroplast development in the green sectors (Wetzel et al ). The lingering question is how do green and color defective sectors develop in the same genotype (Yu et al , Aluru et al , Rosso et al , Zhang et al )?…”