SKL1 Is Essential for Chloroplast Development in Arabidopsis.

Xiaomin Liu,Yanping Jing,Xinwei Wang,Jianwei Xiao,Liwen Zhang,Ruili Li,Shuai Liu,Huimin Xu

doi:10.3389/fpls.2018.00179

Xiaomin Liu, Yanping Jing + Show 6 more

Open Access

https://doi.org/10.3389/fpls.2018.00179

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Abstract

The Arabidopsis shikimate kinase-like 1 (skl1-8) mutant is characterized by a pigment-defective phenotype. Although the related phenotypical defect mainly has been attributed to the blocking of chloroplast development, the molecular functions of SKL1 remain largely unknown. In this study, we combined multiple approaches to investigate the potential functions of SKL1. Results showed that the skl1-8 mutant exhibited an albino phenotype and had dramatically reduced chlorophyll content as a consequence of a single nuclear recessive gene mutation. Chemical complementation analysis indicated that SKL1 does not function as SK enzyme in the shikimate pathway. In addition, by chlorophyll fluorescence parameters and immunoblot analysis, the levels of photosynthetic proteins are substantially reduced. Moreover, by transcriptome analysis, specific groups of nuclear genes involved in photosynthesis, such as light-harvesting complex, pigment metabolism, carbon metabolism, and chloroplast gene expression, were down-regulated, whereas several defense and oxidative stress responsive genes were up-regulated in the skl1-8 mutant compared with the wide type. Furthermore, we found the expression of genes related to auxin transport and response was repressed in the skl1-8 mutant, probable suggesting that SKL1 is involved in auxin-related pathways during chloroplast development. Together, these results provide a useful reference for characterization of SKL1 function during chloroplast biogenesis and development.

Highlights

Chloroplasts are organelles, specialized subunits, in plant and algal cells
We investigated the role of the SKL1, an ortholog of Shikimate kinase (SK) protein located in Arabidopsis chloroplast, which was shown to be responsible for early chloroplast development and plant growth (Fucile et al, 2008)
We found the phenotype and chlorophyll content were dramatically affected in skl1-8 mutant, a feature that highlighted the critical role of SKL1 during early plant development

Summary

Introduction

Chloroplasts are organelles, specialized subunits, in plant and algal cells. The most important role of chloroplast is to conduct photosynthesis and related productions are critical for plant growth (Abdallah et al, 2000; Peltier et al, 2006). The most photosynthetic proteins are nuclear encoded, synthesized in cytoplasm as precursor proteins and being imported into the chloroplast (Inaba and Schnell, 2008), it is has been confirmed that the SKL1 Function in Chloroplast Development disruption on nuclear-encoded and chloroplast-localized proteins can disrupts the chloroplast biogenesis by alternative biological functions, such as chloroplast gene expression, protein import, complexes assembly, lipid biosynthesis and so on (Gutiérrez-Nava et al, 2004; van Wijk, 2015; Zheng et al, 2016; Wang et al, 2017; Zhang Z. et al, 2017). Reported proteins can be roughly classified into three groups based on their potential roles: (i) proteins required for the localization and modification of chloroplast proteins; (ii) enzymes are necessary for the biosynthesis of vitamins, amino acids, fatty acids and nucleotides; and (iii) regulated factors participated in the plastid genes expression (Bryant et al, 2011)

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