Arabidopsis STAY-GREEN2 is a negative regulator of chlorophyll degradation during leaf senescence.
Chlorophyll (Chl) degradation causes leaf yellowing during senescence or under stress conditions. For Chl breakdown, STAY-GREEN1 (SGR1) interacts with Chl catabolic enzymes (CCEs) and light-harvesting complex II (LHCII) at the thylakoid membrane, possibly to allow metabolic channeling of potentially phototoxic Chl breakdown intermediates. Among these Chl catabolic components, SGR1 acts as a key regulator of leaf yellowing. In addition to SGR1 (At4g22920), the Arabidopsis thaliana genome contains an additional homolog, SGR2 (At4g11910), whose biological function remains elusive. Under senescence-inducing conditions, SGR2 expression is highly up-regulated, similarly to SGR1 expression. Here we show that SGR2 function counteracts SGR1 activity in leaf Chl degradation; SGR2-overexpressing plants stayed green and the sgr2-1 knockout mutant exhibited early leaf yellowing under age-, dark-, and stress-induced senescence conditions. Like SGR1, SGR2 interacted with LHCII but, in contrast to SGR1, SGR2 interactions with CCEs were very limited. Furthermore, SGR1 and SGR2 formed homo- or heterodimers, strongly suggesting a role for SGR2 in negatively regulating Chl degradation by possibly interfering with the proposed CCE-recruiting function of SGR1. Our data indicate an antagonistic evolution of the functions of SGR1 and SGR2 in Arabidopsis to balance Chl catabolism in chloroplasts with the dismantling and remobilizing of other cellular components in senescing leaf cells.
Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Yasuhito
Y
Sakuraba
Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea; Present address: Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg, VA 24061, USA.
So-Yon
SY
Park
Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea; Present address: Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup 580-185, Korea.
Ye-Sol
YS
Kim
Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea.
Seung-Hyun
SH
Wang
Department of Plant & Environmental Science, Hankyong National University, Ansung 456-749, Korea.
Soo-Cheul
SC
Yoo
Institute of Plant Biology, University of Zurich, CH-8008 Zurich, Switzerland.
Stefan
S
Hörtensteiner
Department of Plant Science, Plant Genomics and Breeding Institute, Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Korea. Electronic address: ncpaek@snu.ac.kr.
Nam-Chon
NC
Paek
D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016922:Cellular Senescence; D002734:Chlorophyll / Q000378:metabolism*; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D055786:Gene Knockout Techniques; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D010740:Phospholipases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010858:Pigmentation / Q000528:radiation effects; D018515:Plant Leaves / Q000166:cytology*; D013312:Stress, Physiological / Q000528:radiation effects; D020524:Thylakoids / Q000378:metabolism / Q000528:radiation effects
D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D002734:Chlorophyll; D010740:Phospholipases; C455511:SGR2 phospholipase, Arabidopsis
Arabidopsis thaliana; SGR1; SGR2; abiotic stress.; chlorophyll degradation; leaf senescence; stay-green