Translational control in plant stress: the formation of messenger ribonucleoprotein particles (mRNPs) in response to desiccation of Tortula ruralis gametophytes

Abstract

SummaryChanges in gene expression observed in vivo in response to desiccation and rehydration of the desiccation-tolerant bryophyte Tortula ruralis are regulated by alterations in the pattern of selection of messenger RNAs, from a qualitatively constant mRNA pool, by the translational machinery. When drying rates are slow, messenger ribonucleoprotein particles (mRNPs) are formed in the drying gametophytes. A representative rehydrin mRNA, Tr288, was sequestered into these particles which were analysed using sucrose and CsCl gradients. Quantitative RT±PCR analysis of the fractions from a low salt extraction demonstrated that Tr288 mRNA migrated farther in the sucrose gradient, relative to those extractable in high salt, indicating that the transcript is associated with particles that are of higher density. RT±PCR analysis also demonstrated that the majority of Tr288 mRNA, from slowly desiccated gametophytes, is associated with particles that have buoyant densities between 1.44 and 1.64 g cm ± 3 which correspond to the buoyant density range reported for mRNP particles. mRNPs that are unique to drying T. ruralis gametophytes form at least four size classes after in vivo UV cross-linking based upon FPLC analysis. This is the ®rst report of mRNP formation in response to a vegetative water de®cit in plants.

Desiccation Tolerance in the Resurrection PlantCraterostigma plantagineum. A Contribution to the Study of Drought Tolerance at the Molecular Level

“…Here, the major changes in gene expression occur during the first hours of rehydration (Wood and Oliver, 1999). In this case, changes in gene expression in response to dehydration and rehydration are regulated at the translational level, resulting in a change in the complement of mRNAs selected for protein synthesis from a relatively constant mRNA pool (Wood and Oliver, 1999). These findings support the suggestion that desiccation tolerance in bryophytes differs from that in C. plantagineum in being mainly a rehydration-induced cellular repair response (Oliver and Bewley, 1997).…”

“…This is in contrast to observations made on T. ruralis, a representative of the desiccationtolerant bryophytes, which survives rapid desiccation. Here, the major changes in gene expression occur during the first hours of rehydration (Wood and Oliver, 1999). In this case, changes in gene expression in response to dehydration and rehydration are regulated at the translational level, resulting in a change in the complement of mRNAs selected for protein synthesis from a relatively constant mRNA pool (Wood and Oliver, 1999).…”

The translationally repressed pollen-specific ntp303 mRNA is stored in non-polysomal mRNPs during pollen maturation

“…In plants, stored mRNAs encoding storage proteins in alfalfa embryos were found to be sequestered in the form of free mRNPs (Pramanik et al 1992) as well as mRNAs encoding ribosomal proteins in maize embryonic axes (Beltrán-Pena et al 1995). The presence of specific nonpolysomal mRNPs has also been reported in heatstressed carrot (Apuya and Zimmerman 1992) and tomato cells (Stuger et al 1999) and in water-stressed Tortula ruralis gametophytes (Wood and Oliver 1999).…”

Plant Desiccation Tolerance and its Regulation in the Foliage of Resurrection “Flowering-Plant” Species

“…Gaertn., Meyer & Scherb. mRNPs (micro RiboNuceloProteins) accumulate during water loss, and are possibly involved in mRNA storage and protection [131]. This discovery offers a potential mechanism of rapid protein synthesis post-rehydration.…”