Higher plants usually start from seed
germination and re-form seeds after vegetative growth and reproductive
development, thus completing the life cycle. Carbohydrates, lipids, proteins,
mRNA and other macromolecular substances accumulated in seeds are crucial to
maintain the germination potential of seeds, some of which can be preserved for
a long time without degradation, known as long-lived mRNA. In rice, long-lived
mRNA associated with germination began to be transcribed and accumulated 10 to
20 days after flowering, and some long-lived mRNA associated with dormancy and
stress response were transcribed and preserved in cells from 20 days after
flowering to seed maturity. There are many kinds of long-lived mRNA, mainly
including some protein synthesis mRNA, energy metabolism mRNA, cytoskeleton
mRNA and some stress response related mRNA, such as small heat shock protein,
LEA (late embryogenesis abundant) family proteins. Transcriptome analysis found
that the promoter regions of many genes contain ABA- or GA-associated
cis-acting elements, and there are about 500 differentially expressed
long-lived mRNAs in the
Arabidopsis atabi5 (ABA-insensitive 5)
mutant seeds that differ from the wild type, suggestting that abscisic acid
(ABA) and gibberellin (GA) are the key hormones that influence the type of
long-lived mRNA. Long-lived mRNAs are usually cross-linked with a single
ribosome, RNA binding protein, and exists in cells in the form of P-bodies
(PBs) to protect the mRNA from degradation. However, long-lived mRNAs
associated with seed dormancy are gradually degraded during seed post-ripening,
and the oxidative modification of some specific long-lived mRNAs is also a
biological phenomenon to break seed dormancy. During the long-term storage of
seeds, the random degradation of long-lived mRNA is directly related to the
life and vitality of seeds, and the retained mRNA is translated into protein to
help the rapid germination of seeds in the early stage of imbibition. In this
paper, the characteristics and functions of long-lived mRNA were reviewed, and
some scientific issues were raised in order to provide a reference for further
understanding of the molecular mechanisms of seed dormancy, germination and
longevity.