State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.
The New Zealand Institute for Plant and Food Research Ltd, Auckland, 1142, New Zealand.
Plant J. 2023 Dec;116(5):1492-1507. doi: 10.1111/tpj.16444. Epub 2023 Aug 30.
Dihydrochalcones (DHCs) including phlorizin (phloretin 2'-O-glucoside) and its positional isomer trilobatin (phloretin 4'-O-glucoside) are the most abundant phenylpropanoids in apple (Malus spp.). Transcriptional regulation of DHC production is poorly understood despite their importance in insect- and pathogen-plant interactions in human physiology research and in pharmaceuticals. In this study, segregation in hybrid populations and bulked segregant analysis showed that the synthesis of phlorizin and trilobatin in Malus leaves are both single-gene-controlled traits. Promoter sequences of PGT1 and PGT2, two glycosyltransferase genes involved in DHC glycoside synthesis, were shown to discriminate Malus with different DHC glycoside patterns. Differential PGT1 and PGT2 promoter activities determined DHC glycoside accumulation patterns between genotypes. Two transcription factors containing MYB-like DNA-binding domains were then shown to control DHC glycoside patterns in different tissues, with PRR2L mainly expressed in leaf, fruit, flower, stem, and seed while MYB8L mainly expressed in stem and root. Further hybridizations between specific genotypes demonstrated an absolute requirement for DHC glycoside production in Malus during seed development which explains why no Malus spp. with a null DHC chemotype have been reported.
二氢查尔酮（DHC）包括根皮苷（根皮素 2'-O-葡萄糖苷）及其位置异构体三叶苷（根皮素 4'-O-葡萄糖苷）是苹果（Malus spp.）中最丰富的苯丙烷类化合物。尽管 DHC 在昆虫和病原体与植物相互作用、人类生理学研究和药物学中具有重要意义，但它们的生产转录调控仍知之甚少。在这项研究中，杂种群体的分离和混池分析表明，苹果叶片中根皮苷和三叶苷的合成均受单基因控制。参与 DHC 糖苷合成的两个糖基转移酶基因 PGT1 和 PGT2 的启动子序列被证明可以区分具有不同 DHC 糖苷模式的苹果。PGT1 和 PGT2 启动子活性的差异决定了基因型之间 DHC 糖苷的积累模式。然后证明含有 MYB 样 DNA 结合域的两个转录因子控制不同组织中的 DHC 糖苷模式，PRR2L 主要在叶、果实、花、茎和种子中表达，而 MYB8L 主要在茎和根中表达。在特定基因型之间进行进一步杂交表明，在种子发育过程中，DHC 糖苷的产生对苹果来说是绝对必需的，这解释了为什么没有报道过具有空 DHC 化学型的苹果属植物。
