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Resurrection plants employ unique metabolic mechanisms to protect themselves against damage caused by desiccation. This study aimed to identify metabolites, using gas chromatography–mass spectrometry, which were differentially abundant in Eragrostis nindensis at different stages of dehydration and rehydration in leaves which are destined to senesce on desiccation termed “senescent tissue” (ST) and those which remain desiccation-tolerant during water deficit and are termed “non-senescent tissue” (NST). Furthermore, the study compared the shoot and root systems during extreme water deficit and recovery therefrom to unravel similarities and differences at the whole plant level in overcoming desiccation. Shoot metabolomics data showed differentially abundant metabolites in NST, including raffinose, sucrose, glutamic acid, aspartic acid, proline, alpha-ketoglutaric acid, and allantoin, which act as major drivers for plant desiccation tolerance and aid the plant post-rehydration. The metabolites which accumulated in the ST-indicated initiation of programmed cell death (PCD) leading to senescence. The roots accumulated fewer metabolites than the shoots, some exclusive to the root tissues with functions such as osmoprotection, reactive oxygen species quenching, and signaling, and thus proposed to minimize damage in leaf tissues during dehydration and desiccation. Collectively, this work gives further insight into the whole plant responses of E. nindensis to extreme dehydration conditions and could serve as a model for future improvements of drought sensitive crops.

Tripogon loliiformis, an Australian native resurrection grass having an abundant gene pool for combating desiccation, can be the putative model system for functional characterization of stress tolerance genes due to its diploid genome and being a monocotyledonous plant and member of the grass family (Poaceae), like many important cereal crops. For developing callus mediated regeneration from mature grains of Tripogon, Murashige and Skoog medium containing growth regulator, 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.0mgL−1 was the optimum concentration for induction and proliferation of healthy cream calli. Successful regeneration of shoots from callus clumps in MS medium supplemented with 2.0mgL−1 6-benzylaminopurine (BAP) and 0.5mgL−1 α-naphthalene acetic acid (NAA) was obtained from 2 consecutive rounds subculturing of the calli at 3 weeks interval. In addition, rooting needed another 2 rounds within the same media with 2.0mgL−1 BAP but with 0.25mgL−1 NAA. The transient expression of UidA gene at 3 days after Tripogon callus transformation, performed with Agrobacterium tumefaciens strains AGL1 and LBA4404 following rice and Brachypodium distachyon transformation protocols, indicates successful Agrobacterium infection and gene delivery in calli. A stable transformation system for Tripogon loliiformis can be developed near future following the protocols in this study.

Tripogon loliiformis, an Australian native resurrection grass having an abundant gene pool for combating desiccation, can be the putative model system for functional characterization of stress tolerance genes due to its diploid genome and being a monocotyledonous plant and member of the grass family (Poaceae), like many important cereal crops. For developing callus mediated regeneration from mature grains of Tripogon , Murashige and Skoog medium containing growth regulator, 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.0mgL−1 was the optimum concentration for induction and proliferation of healthy cream calli. Successful regeneration of shoots from callus clumps in MS medium supplemented with 2.0mgL−1 6-benzylaminopurine (BAP) and 0.5mgL−1 α-naphthalene acetic acid (NAA) was obtained from 2 consecutive rounds subculturing of the calli at 3 weeks interval. In addition, rooting needed another 2 rounds within the same media with 2.0mgL−1 BAP but with 0.25mgL−1 NAA. The transient expression of UidA gene at 3 days after Tripogon callus transformation, performed with Agrobacterium tumefaciens strains AGL1 and LBA4404 following rice and Brachypodium distachyon transformation protocols, indicates successful Agrobacterium infection and gene delivery in calli. A stable transformation system for Tripogon loliiformis can be developed near future following the protocols in this study. [ABSTRACT FROM AUTHOR]

The majority of flowering-plant species can survive complete air-dryness in their seed and/or pollen. Relatively few species ('resurrection plants') express this desiccation tolerance in their foliage. Knowledge of the regulation of desiccation tolerance in resurrection plant foliage is reviewed. Elucidation of the regulatory mechanism in resurrection grasses may lead to identification of genes that can improve stress tolerance and yield of major crop species. Well-hydrated leaves of resurrection plants are desiccation-sensitive and the leaves become desiccation tolerant as they are drying. Such drought-induction of desiccation tolerance involves changes in gene-expression causing extensive changes in the complement of proteins and the transition to a highly-stable quiescent state lasting months to years. These changes in gene-expression are regulated by several interacting phytohormones, of which drought-induced abscisic acid (ABA) is particularly important in some species. Treatment with only ABA induces desiccation tolerance in vegetative tissue of Borya constricta Churchill. and Craterostigma plantagineum Hochstetter. but not in the resurrection grass Sporobolus stapfianus Gandoger. Suppression of drought-induced senescence is also important for survival of drying. Further research is needed on the triggering of the induction of desiccation tolerance, on the transition between phases of protein synthesis and on the role of the phytohormone, strigolactone and other potential xylem-messengers during drying and rehydration. [ABSTRACT FROM AUTHOR]

ABSTRACTA modification of the ‘cold plaque’ screening technique (Hodge et al., Plant Journal 1992, 2, 257–260) was used to screen a cDNA library constructed from drought-stressed leaf tissue of the desiccation tolerant (‘resurrection’) grass Sporobolus stapfianus. This technique allowed a large number of clones representing genes expressed at low abundance to be isolated. An examination of expression profiles revealed that several of these genes are induced in desiccation-tolerant tissue experiencing severe drought stress. Further characterization indicated that the gene products encoded include an eIF1 protein translation initiation factor and a glycine- and proline-rich protein which have not previously been associated with drought stress. In addition, genes encoding a serine/threonine phosphatase type 2C, a tonoplast-intrinsic protein (TIP) and an early light-inducible protein (ELIP) were isolated. A number of these genes are expressed differentially in desiccation-tolerant and desiccation-sensitive tissues, suggesting that they may be associated with the desiccation tolerance response of S. stapfianus. The results indicate that there may be unique gene regulation processes occurring during induction of desiccation tolerance in resurrection plants which allow different drought-responsive genes to be selectively expressed at successive levels of water loss. [ABSTRACT FROM AUTHOR]

Dry matter productivity under saline conditions was compared in 5 desiccation-tolerant 'resurrection' grasses and one desiccation sensitive species, all in the genus Sporobolus. S. stapfianus was the most salt tolerant, requiring 215 mole NaCl m to reduce shoot dry matter increments to 50% of increments in plants not treated with salt. (This was comparable to published values for the salt tolerant grass Diplachne fusca.) S. lampranthus was salt sensitive, requiring 35 mol m for 50% control yields. S. festivus, S. aff. Fimbriatus, and the deisccation sensitive S.pyramidalis was moderately tolerant (150-170 mol m). The moderate salt resistance of S. aff. fimbriatus was attributed mainly to exclusion of NaCl by roots. Salt export through leaf surfaces was a minor factor. Half of the leaf mesophyll cells survived 50 min immersion in 200 mol NaCl m. Plants of S. aff. fimbriatus and S. pyramidalis tolerated a broad range of soil pH. Plants of 4 desiccation tolerant Sporobolus species survived air-dryness following 3 weeks pretreatment with salinities up to 200 mol m [ABSTRACT FROM AUTHOR]