The Synergistic Mechanism of Photosynthesis and Antioxidant Metabolism between the Green and White Tissues of Ananas comosus var. bracteatus Chimeric Leaves.

Ananas comosus var. bracteatus (Ac. bracteatus) is a typical leaf-chimeric ornamental plant. The chimeric leaves are composed of central green photosynthetic tissue (GT) and marginal albino tissue (AT). The mosaic existence of GT and AT makes the chimeric leaves an ideal material for the study of the synergistic mechanism of photosynthesis and antioxidant metabolism. The daily changes in net photosynthetic rate (NPR) and stomatal conductance (SCT) of the leaves indicated the typical crassulacean acid metabolism (CAM) characteristic of Ac. bracteatus. Both the GT and AT of chimeric leaves fixed CO2 during the night and released CO2 from malic acid for photosynthesis during the daytime. The malic acid content and NADPH-ME activity of the AT during the night was significantly higher than that of GT, which suggests that the AT may work as a CO2 pool to store CO2 during the night and supply CO2 for photosynthesis in the GT during the daytime. Furthermore, the soluble sugar content (SSC) in the AT was significantly lower than that of GT, while the starch content (SC) of the AT was apparently higher than that of GT, indicating that AT was inefficient in photosynthesis but may function as a photosynthate sink to help the GT maintain high photosynthesis activity. Additionally, the AT maintained peroxide balance by enhancing the non-enzymatic antioxidant system and antioxidant enzyme system to avoid antioxidant damage. The enzyme activities of reductive ascorbic acid (AsA) and the glutathione (GSH) cycle (except DHAR) and superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were enhanced, apparently to make the AT grow normally. This study indicates that, although the AT of the chimeric leaves was inefficient at photosynthesis because of the lack of chlorophyll, it can cooperate with the GT by working as a CO2 supplier and photosynthate store to enhance the photosynthetic ability of GT to help chimeric plants grow well. Additionally, the AT can avoid peroxide damage caused by the lack of chlorophyll by enhancing the activity of the antioxidant system. The AT plays an active role in the normal growth of the chimeric leaves.

Systematic identification and comparative analysis of lysine succinylation between the green and white parts of chimeric leaves of Ananas comosus var. bracteatus.

BACKGROUND: Lysine succinylation, an important protein posttranslational modification (PTM), is widespread and conservative. The regulatory functions of succinylation in leaf color has been reported. The chimeric leaves of Ananas comosus var. bracteatus are composed of normal green parts and albino white parts. However, the extent and function of lysine succinylation in chimeric leaves of Ananas comosus var. bracteatus has yet to be investigated. RESULTS: Compared to the green (Gr) parts, the global succinylation level was increased in the white (Wh) parts of chimeric leaves according to the Western blot and immunohistochemistry analysis. Furthermore, we quantitated the change in the succinylation profiles between the Wh and Gr parts of chimeric leaves using label-free LFQ intensity. In total, 855 succinylated sites in 335 proteins were identified, and 593 succinylated sites in 237 proteins were quantified. Compared to the Gr parts, 232 (61.1%) sites in 128 proteins were quantified as upregulated targets, and 148 (38.9%) sites in 70 proteins were quantified as downregulated targets in the Wh parts of chimeric leaves using a 1.5-fold threshold (P < 0.05). These proteins with altered succinylation level were mainly involved in crassulacean acid metabolism (CAM) photosynthesis, photorespiration, glycolysis, the citric acid cycle (CAC) and pyruvate metabolism. CONCLUSIONS: Our results suggested that the changed succinylation level in proteins might function in the main energy metabolism pathways-photosynthesis and respiration. Succinylation might provide a significant effect in the growth of chimeric leaves and the relationship between the Wh and Gr parts of chimeric leaves. This study not only provided a basis for further characterization on the function of succinylated proteins in chimeric leaves of Ananas comosus var. bracteatus but also provided a new insight into molecular breeding for leaf color chimera.

Comparative transcriptomic and proteomic analyses of the green and white parts of chimeric leaves in Ananas comosus var. bracteatus.

BACKGROUND: Ananas comosus var. bracteatus has high ornamental value due to its chimeric leaves. However, the chimeric trait is very unstable in red pineapple plants, and transcriptional variation between the two types of cells (white/green cells) and the molecular mechanism responsible for their albino phenotype remain poorly understood. METHODS: Comparative transcriptomic and proteomic analyses of the white parts (Whs) and green parts (Grs) of chimeric leaves were performed. RESULTS: In total, 1,685 differentially expressed genes (DEGs) (712 upregulated and 973 downregulated) and 1,813 differentially abundant proteins (DAPs) (1,018 with low abundance and 795 with high abundance) were identified. Based on Gene Ontology (Go) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, the DEGs were mostly involved in carbon fixation in photosynthetic organisms, porphyrin and chlorophyll metabolism and oxidative phosphorylation, while proteomic analysis revealed that DAPs were mostly related to ribosomes, photosynthesis, photosynthesis antennas, and porphyrin and chlorophyll metabolism. Combined analysis showed increased mRNA levels but low abundance of nine proteins level in Whs /Grs related to photosynthetic pigment and photosynthesis. Transcriptional changes, posttranscriptional regulation and translational alterations of key enzymes involved in chlorophyll biosynthesis and photosynthesis may play important roles in the albino parts of chimeric leaves.