【求助】关于microRNA的一个小问题

Highly specific gene silencing by artificial microRNAs in Arabidopsis。p1123页中，Figure2.B图中，箭头上方的分数表示什么呢？

:)

Because ARGONAUTE (AGO) proteins cleave targets invariably opposite of positions 10 and 11 of the small RNA (Kasschau et al., 2003), the 5’ ends of small RNAs can be inferred by mapping the cleavage products of their targets (Llave et al., 2002). For targets of amiR-mads-1 (MIR172a backbone), amiR-mads-2 (MIR319a backbone), and amiR-trichome (MIR319a backbone), cleavage products had the expected 5’ ends (Figure 2B). Since uniform cleavage products were obtained even in cases where there was some size heterogeneity in the amiRNA, we conclude that these amiRNAs differed only at their 3’ end.
好好看看这段话

非常感谢版主。我明白了。还有个问题想问：
我想用别的作物（水稻)现成的骨架构建amiRNA转到玉米来研究可以吗？还是非得也再构建一个玉米相关的miRNA做骨架再进行后续的研究呢？由于刚接触这方面的知识，说的不清楚，请指正。

hen hao hen qiangda