Woodson Jesse D, Perez-Ruiz Juan M, Schmitz Robert J, Ecker Joseph R, Chory Joanne
Plant Biology Laboratory, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA, 92037, USA.
Howard Hughes Medical Institute, The Salk Institute, 10010 North Torrey Pines Road, La Jolla, CA, 92037, USA.
Plant J. 2013 Jan;73(1):1-13. doi: 10.1111/tpj.12011. Epub 2012 Nov 5.
Retrograde signalling from plastids to the nucleus is necessary to regulate the organelle's proteome during the establishment of photoautotrophy and fluctuating environmental conditions. Studies that used inhibitors of chloroplast biogenesis have revealed that hundreds of nuclear genes are regulated by retrograde signals emitted from plastids. Plastid gene expression is the source of at least one of these signals, but the number of signals and their mechanisms used to regulate nuclear gene expression are unknown. To further examine the effects of plastid gene expression on nuclear gene expression, we analyzed Arabidopsis mutants that were defective in each of the six sigma factor (SIG) genes that encode proteins utilized by plastid-encoded RNA polymerase to transcribe specific sets of plastid genes. We showed that SIG2 and SIG6 have partially redundant roles in plastid transcription and retrograde signalling to control nuclear gene expression. The loss of GUN1 (a plastid-localized pentatricopeptide repeat protein) is able to restore nuclear (but not plastid) gene expression in both sig2 and sig6, whereas an increase in heme synthesis is able to restore nuclear gene expression in sig2 mutants only. These results demonstrate that sigma factor function is the source of at least two retrograde signals to the nucleus; one likely to involve the transcription of tRNA(Glu) . A microarray analysis showed that these two signals accounted for at least one subset of the nuclear genes that are regulated by the plastid biogenesis inhibitors norflurazon and lincomycin. Together these data suggest that such inhibitors can induce retrograde signalling by affecting transcription in the plastid.
在光自养建立过程和不断变化的环境条件下，从质体到细胞核的逆行信号对于调节细胞器的蛋白质组是必要的。使用叶绿体生物发生抑制剂的研究表明，数百个核基因受质体发出的逆行信号调控。质体基因表达是这些信号中至少一种的来源，但信号的数量及其用于调节核基因表达的机制尚不清楚。为了进一步研究质体基因表达对核基因表达的影响，我们分析了拟南芥突变体，这些突变体在六个sigma因子（SIG）基因中的每一个中都存在缺陷，这些基因编码质体编码的RNA聚合酶用于转录特定质体基因集的蛋白质。我们表明，SIG2和SIG6在质体转录和逆行信号传导以控制核基因表达方面具有部分冗余作用。GUN1（一种定位于质体的五肽重复序列蛋白）的缺失能够恢复sig2和sig6中的核（而非质体）基因表达，而血红素合成的增加仅能恢复sig2突变体中的核基因表达。这些结果表明，sigma因子功能是至少两种向细胞核逆行信号的来源；一种可能涉及tRNA（Glu）的转录。微阵列分析表明，这两种信号至少占了受质体生物发生抑制剂氟草酮和林可霉素调控的核基因子集的一部分。这些数据共同表明，此类抑制剂可通过影响质体中的转录来诱导逆行信号传导。
