Cover Legend Photo of Populus fremontii trees in western Arizona, USA, recently killed by heatwaves and drought. Image courtesy of Hillary Cooper (Moran et al., pp. 2298–2311).
JIPB:中国农大揭示果实成熟过程中乙烯合成的新调控机制
乙烯是影响果实成熟的关键激素。本研究发现了一个quantitative trait locus (QTL)——AFHD，该位点编码了一个NAC家族的转录因子MdNAC18该转录因子的一个直接靶基因是参与乙烯合成的MdACO1. MdNAC18编码区的两个single nucleotide polymorphisms (SNPs) SNP517 and SNP958参与了对MdACO1的激活过程。
在MdACO1启动子中的SNP1229破坏了该基因对靶基因的启动子的结合能力。 SNP517 and SNP958两个SNPs还参与了对MdARF5的表达调控过程，MdARF5诱导了乙烯合成途径中 MdACS1的表达. 除了MdNAC18含有的两个SNPs-SNP517 and SNP958，MdACO1的SNP1229 and SNP769和MdACS1的 InDel162构成了影响苹果成熟的关键遗传变异位点。
小结：本研究解析了转录因子MdNAC18介导的果实成熟机制。
Proposed model showing the functional variation network involved in the genetic control of apple fruit harvest date In early‐ripening apple cultivars or hybrids, MdNAC18 with the SNP517 A and SNP958 G alleles encodes a protein that binds to the promoters of MdNAC18, MdACO1 (with the SNP1229 C allele and the SNP769 T allele), and MdARF5 and activates their transcription. MdARF5 then binds to the promoters of MdACO1 and of MdACS1 to further increase their expression. These transcriptional upregulations result in higher ethylene production rate and early fruit ripening. In late‐ripening apple cultivars or hybrids, the expression levels of MdNAC18, MdACO1, and MdARF5 are lower owing to the weak binding of MdNAC18 encoded by the variant with the SNP517 T and SNP958 A alleles to the promoters of MdNAC18, MdACO1, and MdARF5. The notched solid circle indicates MdNAC18 protein with altered three‐dimensional structure. In addition, the SNP1229 T and SNP769 G alleles in the MdACO1 promoters, as well as InDel162 insertion allele in the MdACS1 promoter, further decrease their expression, resulting in lower ethylene production rate and late fruit ripening.
原文：Natural variations in MdNAC18 exert major genetic effect on apple fruit harvest date by regulating ethylene biosynthesis genes
