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Autophagy mutants show delayed chloroplast development during de-etiolation in carbon limiting conditions

ABSTRACT: Autophagy is a conserved catabolic process that plays an essential role under nutrient starvation condition and influences different developmental processes. We observed that seedlings of autophagy mutants (atg2, atg5, atg7, and atg9) germinated in the dark showed delayed chloroplast development following illumination. The delayed chloroplast development was characterized by a decrease in photosynthetic and chlorophyll biosynthetic proteins, lower chlorophyll content, reduced chloroplast size, and increased levels of proteins involved in lipid biosynthesis. Confirming the biological impact of these differences, photosynthetic performance was impaired in autophagy mutants 12h post illumination. We observed that while gene expression for photosynthetic machinery during de-etiolation was largely unaffected in atg mutants, several genes involved in photosystem assembly were transcriptionally downregulated. We also investigated if the delayed chloroplast development could be explained by lower lipid import to the chloroplast or lower triglyceride (TAG) turnover. We observed that the limitations in the chloroplast lipid import imposed by trigalactosyldiacylglycerol1 are unlikely to explain the delay in chloroplast development. However, we found that lower TAG mobility in the triacylglycerol lipase mutant sugardependent1 significantly affected de-etiolation. Moreover, we showed that lower levels of carbon resources exacerbated the slow-greening phenotype whereas higher levels of carbon resources had an opposite effect. This work suggests a lack of autophagy machinery limits chloroplast development during de-etiolation, and this is exacerbated by limited lipid turnover (lipophagy) that physically or energetically restrains chloroplast development.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE156677 | GEO | 2021/08/04

REPOSITORIES: GEO

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Project description:Purpose: Many studies have demonstrated that ZFPs have important functions in many biological processes, including plant growth and development, stress response, and phytohormone response. RanBP2-type zinc finger transcription factors have been characterized in animals and humans. However, their functions remain largely unknown in plants. Therefore, the functions of RanBP ZFPs in plants need further study to shed new insights into the importance of these transcription factors in developmental processes. Methods: The transcriptomes of between overexpression of SlRBZ transgenic and wild-type tomato by RNA-seq analysis were evaluated using the Illumina HiSeqâ¢ 2000 sequencing platform. Raw sequences were filtered and the resulting sets of clean reads were used for the following analysis by Tophat and DEGseq software. qRTâPCR validation was performed using SYBR Green assays. Results: In this study, we identified a RanBP2-type zinc finger protein gene (SlRBZ) in tomato. SlRBZ was constitutively expressed in roots, stems, leaves, flowers and fruits. Overexpression of SlRBZ resulted in etiolated and dwarf phenotypes in tomato. Determination of physiological index showed that chlorophyll, carotenoid, and GAs contents were evidently decreased in transgenic plants. Furthermore, the qRT-PCR and RNA-Seq analyses demonstrated that the transcription of the genes involved in these biosynthesis pathways obviously decreased in SlRBZ-OE plants. In addition, ultrastructural observation by transmission electron microscopy indicated that plastids could not develop into mature chloroplasts with normal chloroplast membrane and thylakoid membrane system in SlRBZ-OE plants. Conclusions: The results suggest that overexpression of SlRBZ may impair the biosynthesis of chlorophyll, carotenoid, and gibberellin through blocking chloroplast development, resulting in etiolation and dwarfism in tomato. The transcriptomes of between overexpression of SlRBZ transgenic and wild-type tomato by RNA-seq analysis were evaluated, in duplicate, using the Illumina sequencing platform.

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Autophagy mutants show delayed chloroplast development during de-etiolation in carbon limiting conditions

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