File: walley_fpkm.txt
        - expression values for all probes and tissues in 
          Walley et al gene expression study, aligned to 
          B73 v4 gene models.

Reference:
Integration of omic networks in a developmental atlas of maize
Justin W. Walley, Ryan C. Sartor, Zhouxin Shen, Robert J. 
Schmitz, Kevin J. Wu, Mark A. Urich, Joseph R. Nery, Laurie 
G. Smith, James C. Schnable, Joseph. R. Ecker, Steven P. Briggs
Science  19 Aug 2016: Vol. 353, Issue 6301, pp. 814-818
DOI: 10.1126/science.aag1125