Research Projects

Chloroplasts are essential for photosynthesis, a fundamental process that supports life on Earth. Chloroplast biogenesis in green plant tissues involves the proliferation and differentiation of their precursors, known as proplastids, which are undifferentiated organelles present in meristematic or dividing cells. Recent studies have uncovered that chloroplast differentiation aligns with cellular differentiation and occurs in three distinct developmental stages (Loudya et al., 2024a): 1) Proplastid: Involves plastid division, the buildup of import complexes, and plastid DNA replication. 2) Early Plastid: Characterized by increased expression of genes involved in plastid transcription and translation. 3) Photosynthetically Competent Chloroplast: marked by increased expression of photosynthesis-related genes. The majority of chloroplast localized proteins are nucleus-encoded, translated in the cytosol and imported via translocons in the chloroplast envelopes. Among the total chloroplast proteins, only 80 are encoded by the chloroplast DNA (cpDNA), but their synthesis is regulated by nucleus-encoded factors. Any perturbation in plastid protein import, gene expression, or thylakoid biogenesis often results in defective chloroplast development, leading to arrested plant growth or impaired overall plant development. Defects in chloroplast development can be easily detected through altered visual phenotypes, ranging from green to albino, yellow, or pale green tissues. Light plays a major role in chloroplast biogenesis and photosynthesis. To study how light regulates chloroplast development, an elegant genetic screen in Arabidopsis was performed in Joanne Chory’s lab, which identified a line of cab under-expressed mutants (cue1 – cue9) with altered greening phenotype. The current study focuses on cue6, which shows a striking chloroplast development phenotype. The cue6 seedlings develop impaired etioplasts when grown in the dark and display a slow greening phenotype when grown in light conditions. The rosette leaves of cue6 exhibit a notable virescence and partial reticulate phenotype, characterized by a greener midrib, pale-green lamina and leaf margins. An altered greening phenotype that is rescued in the later stages of plant development. Taken together, these observations imply that CUE6 plays an essential role in early plastid development and is crucial for proper chloroplast and leaf development. Therefore, through the proposed study, we aim to expand the understanding of early chloroplast development: (a) confirm the identity of the CUE6 gene through complementation, (b) uncover its role in chloroplast distribution and thylakoid development (ultrastructure) in mesophyll and bundle sheath cells of leaf lamina and midrib (c) identify the molecular mechanism by investigating the interactome of CUE6 and d) global gene expression analysis. Certainly, this study will identify a candidate and its role in overall chloroplast development.