Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, NO. 1 Road, Qianhuhou Villiage, Xuanwu District, Nanjing 210014, China.
Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, NO. 1 Road, Qianhuhou Villiage, Xuanwu District, Nanjing 210014, China.
Tree Physiol. 2024 May 5;44(5). doi: 10.1093/treephys/tpae040.
Grafting is a widely used technique for pecan propagation; however, the background molecular events underlying grafting are still poorly understood. In our study, the graft partners during pecan [Carya illinoinensis (Wangenh.) K. Koch] graft union formation were separately sampled for RNA-seq, and the transcriptional dynamics were described via weighted gene co-expression network analysis. To reveal the main events underlying grafting, the correlations between modules and grafting traits were analyzed. Functional annotation showed that during the entire graft process, signal transduction was activated in the scion, while messenger RNA splicing was induced in the rootstock. At 2 days after grafting, the main processes occurring in the scion were associated with protein synthesis and processing, while the primary processes occurring in the rootstock were energy release-related. During the period of 7-14 days after grafting, defense response was a critical process taking place in the scion; however, the main process functioning in the rootstock was photosynthesis. From 22 to 32 days after grafting, the principal processes taking place in the scion were jasmonic acid biosynthesis and defense response, whereas the highly activated processes associated with the rootstock were auxin biosynthesis and plant-type secondary cell wall biogenesis. To further prove that the graft partners responded asymmetrically to stress, hydrogen peroxide contents as well as peroxidase and β-1,3-glucanase activities were detected, and the results showed that their levels were increased in the scion not the rootstock at certain time points after grafting. Our study reveals that the scion and rootstock might respond asymmetrically to grafting in pecan, and the scion was likely associated with stress response, while the rootstock was probably involved in energy supply and xylem bridge differentiation during graft union formation.
嫁接是一种广泛应用于山核桃繁殖的技术；然而，嫁接背后的分子事件基础仍知之甚少。在我们的研究中，在山核桃 [Carya illinoinensis (Wangenh.) K. Koch] 嫁接形成过程中，分别对嫁接伙伴进行了 RNA-seq 采样，并通过加权基因共表达网络分析描述了转录动态。为了揭示嫁接的主要事件，分析了模块与嫁接性状之间的相关性。功能注释表明，在整个嫁接过程中，信号转导在接穗中被激活，而信使 RNA 剪接在砧木中被诱导。在嫁接后 2 天，接穗中发生的主要过程与蛋白质合成和加工有关，而砧木中发生的主要过程与能量释放有关。在嫁接后 7-14 天期间，防御反应是接穗中发生的关键过程；然而，在砧木中起主要作用的过程是光合作用。从嫁接后 22 天到 32 天，接穗中的主要过程是茉莉酸生物合成和防御反应，而与砧木相关的高度激活过程是生长素生物合成和植物型次生细胞壁生物发生。为了进一步证明嫁接伙伴对胁迫的反应不对称，检测了过氧化氢含量以及过氧化物酶和β-1,3-葡聚糖酶的活性，结果表明在嫁接后某些时间点，过氧化氢含量以及过氧化物酶和β-1,3-葡聚糖酶的活性在接穗中增加，而不在砧木中增加。我们的研究表明，在山核桃中，接穗和砧木可能对嫁接表现出不对称的反应，接穗可能与应激反应有关，而砧木可能参与嫁接过程中能量供应和木质部桥接分化。
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