大背景：Cassava storage roots are among the most important root crops worldwide and represent one of the most consumed staple foods in Sub-Saharan Africa. 

小背景：The vegetatively propagated tropical shrub can form many starchy tuberous roots from its stem. These storage roots are formed through the activation of secondary root growth processes. 

提出问题：However, the underlying genetic regulation of storage root development is largely unknown.

主要研究：Here we report on distinct structural and transcriptional changes occurring during the early phases of storage root development.

结果1-生长素：A pronounced increase in auxin-related transcripts and the transcriptional activation of secondary growth factors, as well as a decrease in gibberellin-related transcripts was observed during the early stages of secondary root growth. 

结果2-细胞壁合成：This was accompanied by increased cell wall biosynthesis, increased most notably during the initial xylem expansion within the root vasculature. 

结果3-维管形成层：Starch storage metabolism was activated only after the formation of the vascular cambium. 

结果4-相关基因：The formation of non-lignified xylem parenchyma cells and the activation of starch storage metabolism coincided with increased expression of the KNOX/BEL genes KNAT1, PENNYWISE and POUND-FOOLISH, indicating their importance for proper xylem parenchyma function.

 摘 要 

木薯的贮藏根茎是世界上最重要的根茎作物之一，是亚撒哈拉地区消耗量最大的主食之一。热带灌木的营养繁殖可以从茎上形成许多含淀粉的块根。这些贮藏根是通过激活次生根生长过程而形成的。但是，贮藏根发育的潜在遗传调控尚不清楚。本文中，作者报道了贮藏根发育早期的不同结构和转录变化。在次生根生长的早期阶段，作者观察到了生长素相关转录本和次生生长因子的转录激活显著增加，而赤霉素相关转录本减少。同时，这伴随着细胞壁生物合成的增加，在根的维管系统内木质部原始细胞扩张期间增加最为显著。淀粉贮藏代谢只有在维管形成层形成后才会被激活。非木质化木质部薄壁细胞的形成和淀粉贮藏代谢的激活与KNOX/BEL类基因KNAT1、PENNYWISE和POUND-FOOLISH的表达量增加相一致，表明其对木质部薄壁组织发挥功能具有非常重的作用。