Disruption of carotene biosynthesis leads to abnormal plastids and variegated leaves in Brassica napus

Abstract

Leaf color is an important characteristic of normal chloroplast development. Variegated plants have green-and white-sectored leaves, which can be used to identify important pathways and molecular mechanisms of chloroplast development. We studied two Brassica napus variegation mutants from same one variegated ancestor, designated ZY-4 and ZY-8, which have different degrees of variegation. When grown in identical conditions, the ratio of white sectors in ZY-4 leaves is higher than in ZY-8. In both mutants, the cells in green sectors contain normal chloroplasts; while, the cells in white sectors contain abnormal plastids. Seedling chloroplasts ultrastructure of both mutants showed that the biogenesis of chloroplasts was blocked in early stages; delayed development and structual damage in ZY-4 were more serious than in ZY-8. Employing bulked segregant analysis(BSA), two bulks (BY142 and BY137) from BC 2 F 1 lines derived from ZY-4 and ZS11, and one bulk (BY56) from BC 2 F 1 lines derived from ZY-8 and ZS11, and screening by Brassica 60K SNP BeadChip Array, showed the candidate regions localized in chromosome A08 (BY142), C04 (BY137), and A08 (BY56), respectively. Transcriptome analysis of five seedling development stages of ZY-4, ZY-8, and ZS11 showed that photosynthesis, energy metabolism-related pathways and translation-related pathways were important for chloroplast biogenesis. The number of down-or up-regulated genes related to immune system process in ZY-4 was more than in ZY-8. The retrograde signaling pathway was mis-regulated in both mutants. DEG analysis indicated that both mutants showed photooxidative damages. By coupling transcriptome and BSA CHIP analyses, some candidate genes were identified. The gene expression pattern of carotene biosynthesis pathway was disrupted in both mutants. However, histochemical analysis of ROS revealed that there was no excessive accumulation of ROS in ZY-4 and ZY-8. Taken together, our data indicate that the disruption of carotene biosynthetic pathways leads to the variegation phenotypes of ZY-4 and ZY-8 and there are some functions that can compensate for the disruption of carotene biosynthesis in ZY-4 and ZY-8 to reduce ROS and prevent seedling mortality.

Lycopene β-cyclase expression influences plant physiology, development, and metabolism in tobacco plants

“…By contrast, the reduced NtLCYB expression caused leaf variegation in the RNAi lines, as reported for other mutants in Arabidopsis, Brassica napus, and rice, with defects in carotenoid biosynthesis (Aluru et al, 2001;Aluru et al, 2009;Fang et al, 2008;Zhao et al, 2020).…”

“…S4B-D), points towards pigment, photosynthesis, and chloroplast biogenesis defects in these lines. Moreover, other carotenoid-defective mutants, and specially pds3 mutants, showed impaired chloroplast differentiation, development, and reduced chloroplast number (Aluru et al, 2001;Qin et al, 2007;Zhao et al, 2020). Carotenoids are located in the photosynthetic membrane in the form of chlorophyll-carotenoid-protein complexes and some carotenogenic enzymes are membraneassociated (Cunningham and Gantt, 1998;Green and Durnford, 1996).…”

“…11E), might explain the reduced growth phenotype. In fact, altered chloroplast ultrastructure and development were observed in other mutants with reduced expression of other carotenoid genes (PDS, ZDS, CRTISO), with mutant lines also showing impaired or delayed growth (Aluru et al, 2001;Aluru et al, 2009;Fang et al, 2008;Qin et al, 2007;Zhao et al, 2020).…”

Cytological and Transcriptomic Analysis Provide Insights into the Formation of Variegated Leaves in Ilex × altaclerensis ‘Belgica Aurea’

“…In Cymbidium sinense , the ethylene response factors (ERFs) gene CsERF2 played crucial roles in leaf variegation [ 13 ]. Moreover, data showed that disruption of carotene biosynthesis in Brassica napus also led to abnormal plastids and variegated leaves [ 14 ].…”

Vegetação inside: uma análise comparativa de pigmentos foliares e fluorescência da clorofila em plantas variegadas

“…The analyzed species had higher Chla contents than any other photosynthetic pigment (Figure 2). This fact is widely discussed in several studies [5,[17][18][19][20][21] since Chla operates as the central molecule responsible for capturing light energy. This way, it can boost the electron transport reactions in the first stage of photosynthesis [19].…”