Table_1_Enhanced Conjugation of Auxin by GH3 Enzymes Leads to Poor Adventitious Rooting in Carnation Stem Cuttings.DOCX

Commercial carnation (Dianthus caryophyllus) cultivars are vegetatively propagated from axillary stem cuttings through adventitious rooting; a process which is affected by complex interactions between nutrient and hormone levels and is strongly genotype-dependent. To deepen our understanding of the regulatory events controlling this process, we performed a comparative study of adventitious root (AR) formation in two carnation cultivars with contrasting rooting performance, “2101–02 MFR” and “2003 R 8”, as well as in the reference cultivar “Master”. We provided molecular evidence that localized auxin response in the stem cutting base was required for efficient adventitious rooting in this species, which was dynamically established by polar auxin transport from the leaves. In turn, the bad-rooting behavior of the “2003 R 8” cultivar was correlated with enhanced synthesis of indole-3-acetic acid conjugated to aspartic acid by GH3 proteins in the stem cutting base. Treatment of stem cuttings with a competitive inhibitor of GH3 enzyme activity significantly improved rooting of “2003 R 8”. Our results allowed us to propose a working model where endogenous auxin homeostasis regulated by GH3 proteins accounts for the cultivar dependency of AR formation in carnation stem cuttings.

商业栽培香石竹（Dianthus caryophyllus，康乃馨）品种通过腋生茎插条的不定根（adventitious root, AR）形成过程实现无性繁殖；该过程受营养与激素水平间的复杂互作调控，且高度依赖基因型。为深入解析调控该过程的分子调控事件，本研究选取生根表现迥异的两个康乃馨栽培品种‘2101–02 MFR’与‘2003 R 8’，并以参考品种‘Master’为对照，开展不定根形成的比较研究。本研究提供分子证据证实，该物种实现高效不定根形成依赖于插条基部的局部生长素（auxin）响应，而该响应由叶片来源的生长素极性运输动态建立。进一步发现，‘2003 R 8’品种的生根不良表型与其插条基部GH3蛋白介导的吲哚-3-乙酸（indole-3-acetic acid, IAA）与天冬氨酸结合物的合成增强显著相关。采用GH3酶活性竞争性抑制剂处理插条，可显著改善‘2003 R 8’的生根能力。基于上述研究结果，本研究提出工作模型：由GH3蛋白调控的内源生长素稳态，是康乃馨茎插条不定根形成存在品种依赖性的核心调控机制。