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<p>Chloroplast development requires a concerted function of the protein quality control system, in which several chloroplast proteases act as critical regulators. The Site-2 protease Ethylene-dependent Gravitropism-deficient and Yellow-green 1 (EGY1) is one such regulator, and loss of EGY1 causes pleiotropic defects in chloroplast function. We performed an EMS-based suppressor screen using the <i>egy1-3</i> mutant to identify the components functionally linked to EGY1. This screen identified a suppressor carrying a G139S substitution in Stay Green 1 (SGR1), an Mg-dechelatase that initiates chlorophyll degradation. The G139S substitution impaired SGR1 activity and suppressed multiple characteristic phenotypes of the <i>egy1</i> mutant, including reduced chlorophyll accumulation, accelerated leaf senescence, and defective chloroplast development in guard cells. In contrast, another stay-green mutant, <i>pph</i>, did not suppress the <i>egy1</i> phenotype, indicating that the suppression was specific to SGR1 loss. These findings provide independent genetic support for the previously proposed regulatory relationship between EGY1 and SGR1. Our results also suggest that SGR1 contributes to chloroplast development in addition to its established role in senescence.</p>

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Genetic Suppressor Screening Identified an SGR1 Mutation that Suppresses Pleiotropic Defects in Arabidopsis egy1 Mutant

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Yuki Karasaki,
  • Yanghee Kim,
  • Kenta Maezaka,
  • Yusuke Kato

摘要

Chloroplast development requires a concerted function of the protein quality control system, in which several chloroplast proteases act as critical regulators. The Site-2 protease Ethylene-dependent Gravitropism-deficient and Yellow-green 1 (EGY1) is one such regulator, and loss of EGY1 causes pleiotropic defects in chloroplast function. We performed an EMS-based suppressor screen using the egy1-3 mutant to identify the components functionally linked to EGY1. This screen identified a suppressor carrying a G139S substitution in Stay Green 1 (SGR1), an Mg-dechelatase that initiates chlorophyll degradation. The G139S substitution impaired SGR1 activity and suppressed multiple characteristic phenotypes of the egy1 mutant, including reduced chlorophyll accumulation, accelerated leaf senescence, and defective chloroplast development in guard cells. In contrast, another stay-green mutant, pph, did not suppress the egy1 phenotype, indicating that the suppression was specific to SGR1 loss. These findings provide independent genetic support for the previously proposed regulatory relationship between EGY1 and SGR1. Our results also suggest that SGR1 contributes to chloroplast development in addition to its established role in senescence.