![]() ![]() Protein homeostasis (proteostasis) in chloroplasts, maintained by a balance between protein import form cytosol, synthesis and degradation within chloroplasts, is essential for its functions during plant growth, development, and stress resistance ( Sun et al., 2021). Light-independent chloroplast development requires the expression of hundreds of chloroplast-related genes and photosynthesis associated nuclear genes. The plastid retains a functional genome which encodes about 100 proteins, while most of the other ∼2,000–3,000 proteins within chloroplasts are imported from the cytosol via the translocon at the outer envelope membrane of chloroplasts (TOC) and translocon at the inner envelope membrane of chloroplasts (TIC) systems ( Li and Chiu, 2010 Jarvis and Lopez-Juez, 2013). Upon light, the biogenesis of thylakoids begins immediately accompanied by the coordinated synthesis and assembly of proteins, chlorophylls and lipids in both space and time ( Cackett et al., 2021). Chloroplasts in de-etiolated plants are developed from proplastids which are small and undifferentiated plastids. Together, our data demonstrates that FtsHi5/TSL2 plays an important role in chloroplast development and protein accumulation in chloroplasts, especially at low environmental temperatures in Arabidopsis.Ĭhloroplast biogenesis affects plant growth and development due to its functions in photosynthesis and biosynthesis of amino acids, fatty acids, nucleotides, and phytohormones ( Neuhaus and Emes, 2000). Quantitative mass spectrometry analysis with Tandem Mass Tag (TMT) isobaric labeling revealed broad changes in the chloroplast proteome of tsl2 mutant plants at low temperature, which is agreed with the impaired chloroplast biogenesis and function in tsl2 plants. Genetic complementation analysis confirmed that complemented expression of FtsHi5 rescued the chlorophyll content and thylakoid development defects observed in tsl2 mutants at 16☌. ![]() Bulk Segregant Analysis (BSA) revealed that TSL2 encodes FtsH-Inactive Protein 5 (FtsHi5). The tsl2 mutant showed a weak yellowish phenotype at normal growth temperature (22☌), and the phenotype was more pronounced at low growth temperature (16☌) and largely rescued at high growth temperature (29☌). Here, a temperature-conditioned chloroplast development defective mutant thermo- sensitive mutant in leaf color 2 ( tsl2) of Arabidopsis was obtained through a forward genetic screening. However, the molecular mechanism of how plants coordinate chloroplast development and environmental temperature changes remains largely unknown. The growth and development of plants are very sensitive to environmental temperature changes, and chloroplast development is also regulated by adverse environmental temperatures. Chloroplasts are indispensable for higher plants. ![]()
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