Han Yafan, Lu Rui, Yan Danni, Liu Zhongchi, Luo Xi, Kang Chunying
National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan, 430070, China.
Hubei Hongshan Laboratory, Wuhan, 430070, China.
Plant Physiol. 2025 Apr 16. doi: 10.1093/plphys/kiaf156.
Leaf morphology affects physiological activities and contributes to environment adaptation. The phytohormones auxin and cytokinin both regulate leaf shape, but how they act together to specify leaf complexity is not fully understood. In woodland strawberry (Fragaria vesca), the wild type develops trifoliate leaves, whereas myb117a mutants produce one to five leaflets with fewer serrations. Transcriptome analysis revealed that the auxin biosynthesis gene YUCCA4 (FveYUC4), the cytokinin biosynthesis gene ISOPENTENYL TRANSFERASE2 (FveIPT2), the cytokinin degradation gene CYTOKININ OXIDASE/DEHYDROGENASE1 (FveCKX1), and the transcription factor gene CUP-SHAPED COTYLEDON2 (FveCUC2a) are altered in the myb117a mutant. Accordingly, the myb117a leaves contain lower auxin levels and higher cytokinin levels compared to wild type. Moreover, treatment with the auxin transport inhibitor NPA produced simple leaves with smooth margins, whereas exogenous cytokinin application resulted in a higher percentage of four to five leaflets in myb117a. Several lines of evidence showed that FveMYB117a can directly bind to the promoters of FveYUC4 and FveCUC2a and influence their expression. Both myb117a yuc4 and myb117a cuc2a double mutants had fewer leaflets with greatly reduced or no serrations compared to myb117a, suggesting that these genes function in the same pathway. Overall, our results indicate that FveMYB117a is a transcription factor that coordinates auxin and cytokinin homeostasis in young leaves, thereby contributing to robust leaf morphogenesis in strawberry.
叶片形态影响生理活动并有助于适应环境。植物激素生长素和细胞分裂素都调节叶片形状，但它们如何共同作用来确定叶片的复杂性尚不完全清楚。在森林草莓（Fragaria vesca）中，野生型发育出三出复叶，而myb117a突变体产生一到五片小叶，锯齿较少。转录组分析表明，生长素生物合成基因YUCCA4（FveYUC4）、细胞分裂素生物合成基因异戊烯基转移酶2（FveIPT2）、细胞分裂素降解基因细胞分裂素氧化酶/脱氢酶1（FveCKX1）和转录因子基因杯状子叶2（FveCUC2a）在myb117a突变体中发生了改变。因此，与野生型相比，myb117a叶片中的生长素水平较低，细胞分裂素水平较高。此外，用生长素运输抑制剂NPA处理产生了边缘光滑的单叶，而外源施用细胞分裂素导致myb117a中四到五片小叶的比例更高。多项证据表明，FveMYB117a可以直接结合FveYUC4和FveCUC2a的启动子并影响它们的表达。与myb117a相比，myb117a yuc4和myb117a cuc2a双突变体的小叶数量更少，锯齿大大减少或没有锯齿，这表明这些基因在同一途径中发挥作用。总体而言，我们的结果表明，FveMYB117a是一种转录因子，可协调幼叶中生长素和细胞分裂素的稳态，从而有助于草莓叶片的稳健形态发生。
