Table_1_A high trans-zeatin nucleoside concentration in corms may promote the multileaf growth of Amorphophallus muelleri.xlsx

Amorphophallus muelleri has a multileaf growth pattern different from that of other konjacs; however, the hormonal mechanism underlying this phenomenon is not clear. In this study, the levels of hormones closely related to the sprouting of the axillary bud, including five types of cytokinins, indole-3-acetic acid (IAA) and abscisic acid (ABA) were measured. In the second leaf sprouting stage, the content of trans-zeatin riboside (tZR) in corms increased more than 5000-fold over that in the dormancy period. Surprisingly, although the expression of CYP735A1 and CYP735A2, which synthesize the precursors for tZR was elevated at the second leaf sprouting stage, the expression of IPTs, which have key roles in cytokinin biosynthesis, did not change significantly. In addition, most cytokinin contents in leaves during the same period were significantly lower than those in corms. We speculate that the high cytokinin contents in the corms may not biosynthesized de novo in corms. In addition, the IAA content in the corms also considerably increased during the second leaf sprouting stage. Indole-3-acetaldehyde oxidase (AO1) and auxin efflux carrier PIN1A, presented relatively high expression levels in the same period. In contrast, ABA content, and the expression of NCED1, a rate-limiting enzyme in ABA biosynthesis, were suppressed at the second leaf sprouting stage. It is worth mentioning that N6-(Δ2-isopentenyl) adenosine (iP)-type cytokinins have a high content in corms in the dormant period that significantly decreases after the first leaf sprouting stage, which is completely different from the trend of tZR. By treating dormant corms with iP, the percentage of multibud plants increased, and the growth performance in terms of bud and root length was significantly higher than those of the control. This implies that iP-type cytokinins tend to play a role in promoting first seedling sprouting. Furthermore, there was a remarkable increase of the IAA content in both corms and roots under iP treatment but an inhibitory effect in buds. We speculate that the increase in the IAA content induced by iP is tissue specific. These results will assist in the understanding of the role of hormones, especially cytokinins, in the multileaf growth type of konjac.

穆勒魔芋（Amorphophallus muelleri）具有区别于其他魔芋（konjac）的多叶生长模式，但其背后的激素调控机制尚未阐明。本研究检测了与腋芽萌发密切相关的激素水平，包括5类细胞分裂素、吲哚-3-乙酸（IAA）以及脱落酸（ABA）。在第二叶萌发阶段，球茎内反式玉米素核苷（tZR）的含量较休眠期提升超过5000倍。令人意外的是，尽管合成tZR前体的CYP735A1与CYP735A2的表达在第二叶萌发阶段上调，但在细胞分裂素生物合成中发挥关键作用的IPT基因的表达并无显著变化。此外，同期叶片中的多数细胞分裂素含量显著低于球茎。我们推测，球茎内的高细胞分裂素含量可能并非在球茎中从头合成。

与此同时，第二叶萌发阶段球茎内的IAA含量也显著升高。吲哚-3-乙醛氧化酶（AO1）与生长素输出载体PIN1A在该时期呈现较高的表达水平。与之相反，ABA含量以及ABA生物合成限速酶NCED1的表达在第二叶萌发阶段受到抑制。

值得注意的是，N6-(Δ2-异戊烯基)腺苷（iP）型细胞分裂素在休眠期球茎中含量较高，但在第一叶萌发阶段后显著下降，这一趋势与tZR完全相反。通过iP处理休眠球茎，多芽植株的比例提升，且芽与根的长度生长性能显著优于对照组。这表明iP型细胞分裂素倾向于促进首次幼苗萌发。

此外，经iP处理后，球茎与根内的IAA含量显著升高，但芽内的IAA含量却受到抑制。我们推测，iP诱导的IAA含量升高具有组织特异性。上述研究结果将有助于理解激素（尤其是细胞分裂素）在魔芋多叶生长类型中的作用。