Two new proteins, RICE1 and RICE2, were discovered by a team of researchers
led by biochemist Dr. Xiuren Zhang from Texas A&M AgriLife Research. The
proteins could help study better ways to regulate plant structure and the
ability to resist crop stresses such as drought.

Dr. Zhang said that understanding RNA silencing is important so that
researchers can use the technique to help a plant overcome barriers to
growth or ability to deal with unfavorable environments by tweaking the
amount of RNA. A key player in RNA silencing is RISC (RNA-induced Silencing
Complex), which contains microRNA and enzymes called AGOs. "MicroRNA starts
as twins, so to speak, but one of the twins leaves and disappears when AGO
protein moves in," Zhang said.

Using proteomic analysis, Dr. Zhang and colleagues deciphered the
constituents of one kind of RISC in Arabidopsis and found proteins RICE, or
RISC-Interacting Clearing Exoribonuclease. RICE1 was found to have a
ring-like structure with six identical molecules. Analysis of the shape of
RICE1 revealed its active region which is responsible for degrading RNA
fragments, hidden on the adjacent site of two RICE molecules.



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