Li Guofang, Ma Juanjuan, Tan Ming, Mao Jiangping, An Na, Sha Guangli, Zhang Dong, Zhao Caiping, Han Mingyu
College of Horticulture, Northwest A & F University, Yangling, Shaanxi, 712100, China.
Institute of agricultural science, Qingdao, Shandong, 266000, China.
BMC Genomics. 2016 Feb 29;17:150. doi: 10.1186/s12864-016-2484-x.
The root architecture of grafted apple (Malus spp.) is affected by various characteristics of the scions. To provide information on the molecular mechanisms underlying this influence, we examined root transcriptomes of M. robusta rootstock grafted with scions of wild-type (WT) apple (M. spectabilis) and a more-branching (MB) mutant at the branching stage.
The growth rate of rootstock grafted MB was repressed significantly, especially the primary root length and diameter, and root weight. Biological function categories of differentially expressed genes were significantly enriched in processes associated with hormone signal transduction and intracellular activity, with processes related to the cell cycle especially down-regulated. Roots of rootstock grafted with MB scions displayed elevated auxin and cytokinin contents and reduced expression of MrPIN1, MrARF, MrAHP, most MrCRE1 genes, and cell growth-related genes MrGH3, MrSAUR and MrTCH4. Although auxin accumulation and transcription of MrPIN3, MrALF1 and MrALF4 tended to induce lateral root formation in MB-grafted rootstock, the number of lateral roots was not significantly changed. Sucrose, fructose and glucose contents were not decreased in MB-grafted roots compared with those bearing WT scions, but glycolysis and tricarboxylic acid cycle metabolic activities were repressed. Root resistance and nitrogen metabolism were reduced in MB-grafted roots as well.
Our findings suggest that root growth and development of rootstock are mainly influenced by sugar metabolism and auxin and cytokinin signaling pathways. This study provides a basis that the characteristics of scions are related to root growth and development, resistance and activity of rootstocks.
嫁接苹果（苹果属）的根系结构受接穗的各种特性影响。为了提供关于这种影响潜在分子机制的信息，我们在分枝阶段检测了用野生型（WT）苹果（山荆子）和一个多分枝（MB）突变体的接穗嫁接的健壮苹果砧木的根系转录组。
嫁接MB的砧木生长速率显著受到抑制，尤其是主根长度、直径和根重量。差异表达基因的生物学功能类别在与激素信号转导和细胞内活性相关的过程中显著富集，与细胞周期相关的过程尤其下调。嫁接MB接穗的砧木根系显示生长素和细胞分裂素含量升高，以及MrPIN1、MrARF、MrAHP、大多数MrCRE1基因和细胞生长相关基因MrGH3、MrSAUR和MrTCH4的表达降低。尽管生长素积累以及MrPIN3、MrALF1和MrALF4的转录倾向于诱导MB嫁接砧木上侧根的形成，但侧根数量没有显著变化。与带有WT接穗的根系相比，嫁接MB的根系中蔗糖、果糖和葡萄糖含量没有降低，但糖酵解和三羧酸循环代谢活性受到抑制。嫁接MB的根系的根抗性和氮代谢也降低。
我们的研究结果表明，砧木的根系生长和发育主要受糖代谢以及生长素和细胞分裂素信号通路的影响。本研究为接穗特性与砧木根系生长发育、抗性和活性相关提供了依据。
