RNA quality control systems identify and degrade aberrant mRNAs, thereby preventing
the accumulation of faulty proteins. Non-stop decay (NSD) and No-go decay (NGD) are
closely related RNA quality control systems that act during translation. NSD degrades
mRNAs lacking a stop codon, while NGD recognizes and decays mRNAs that contain translation
elongation inhibitory structures. NGD has been intensively studied in yeast and animals
but it has not been described in plants yet. In yeast, NGD is induced if the elongating
ribosome is stalled by a strong inhibitory structure. Then, the mRNA is cleaved by
an unknown nuclease and the cleavage fragments are degraded. Here we show that NGD
also operates in plant. We tested several potential NGD cis-elements and found that
in plants, unlike in yeast, only long A-stretches induce NGD. These long A-stretches
trigger endonucleolytic cleavage, and then the 5' fragments are degraded in a Pelota-,
HBS1- and SKI2- dependent manner, while XRN4 eliminates the 3' fragment. We also show
that plant NGD operates gradually, the longer the A stretch, the more efficient the
cleavage. Our data suggest that mechanistically NGD is conserved in eukaryotes, although
the NGD inducing cis-elements could be different. Moreover, we found that Arabidopsis
AtPelota1 functions in both NGD and NSD, while AtPelota2 represses these quality control
systems. The function of plant NGD will be discussed.
