Abstract
Leaf coloration is one of the most important and attractive characteristics of Ananas comosus var. bracteatus. The chimeric character is not stable during the in vitro tissue culturing. Many regenerated plants lost economic values for the loss of the chimeric character of leaves. In order to reveal the molecular mechanisms involved in the albino phenotype of the leaf cells, the physiological and transcriptional differences between complete white (CWh) and green (CGr) leaf cells of A. comosus var. bracteatus were analyzed. A total of 1,431 differentially expressed unigenes (DEGs) in CGr and CWh leaves were identified using RNA-seq. A comparison to the COG, GO and KEGG annotations revealed DEGs involved in chlorophyll biosynthesis, chloroplast development and photosynthesis. Furthermore, the measurement of main precursors of chlorophyll in the CWh leaves confirmed that the rate-limiting step in chlorophyll biosynthesis, and thus the cause of the albino phenotype of the white cells, was the conversion of pyrrole porphobilinogen (PBG) to uroporphyrinogen III (Uro III). The enzyme activity of porphobilinogen deaminase (PBGD) and uroporporphyrinogn III synthase (UROS), which catalyze the transition of PBG to Uro III, was significantly decreased in the CWh leaves. Our data showed the transcriptional differences between the CWh and CGr plants and characterized key steps in chlorophyll biosynthesis of the CWh leaves. These results contribute to our understanding of the mechanisms and regulation of pigment biosynthesis in the CWh leaf cells of A. comosus var. bracteatus.
Highlights
Pineapple is an herbaceous perennial monocot that belongs to the Bromeliaceae family
Pineapple carries out crassulacean acid metabolism (CAM), known as CAM photosynthesis, and more recently the pineapple genome sequence and the expression and regulations of the genes associated with CAM were analyzed [9]
The complete white (CWh) and CGr Ananas comosus var. bracteatus tissue culture plants were derived from chimera plants using our previously published protocol [11]
Summary
Pineapple is an herbaceous perennial monocot that belongs to the Bromeliaceae family. Plants of this family are native to South America and are cultivated commercially for their fruit, and the high-quality silk fiber of their stem and leaves [1, 2]. These plants are a source of bromelain, which is a proteolytic enzyme complex used in the meat industry for its health benefits. A large number of secondary metabolites have been synthesized from Ananas leaves and fruit infusions [4,5,6,7,8]. Pineapple carries out crassulacean acid metabolism (CAM), known as CAM photosynthesis, and more recently the pineapple genome sequence and the expression and regulations of the genes associated with CAM were analyzed [9]
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