Low RNA yield in dual RNA/DNA extraction - (Mar/18/2015 )

Hi all,

A student in our lab has been working for two months to develop a working protocol for DNA-RNA dual extraction. She's tried Qiagen and Zymo kits, and decided that the Qiagen Allprep dual extraction kit was the better option. She tried the protocol out on honey bee abdominal tissue for practice, and it turned out with good RNA and DNA yields. However, she's now started extractions from a different species that she collected in South America (so the samples are irreplaceable), and her RNA yields have been a total crapshoot. For some, she's getting as much as 5 micrograms, and for others, she's getting 300 ng total, and some samples are so low their yield is essentially nil. She's following the AllPrep protocol to the nth degree, and per the recommendation of Qiagen, replaced the RLT Plus with regular RLT buffer from the RNeasy kit. Her DNA yields have been fine, so it's the RNA yields that are a major issue. Does anyone have any advice on this? Thanks!

how are the samples collected and stored? it's possible that the rna is degraded.