Shared up-regulation and contrasting down-regulation of gene expression distinguish desiccation-tolerant from intolerant green algae

Among green plants, desiccation tolerance is common in seeds and spores but rare in leaves and other vegetative green tissues. Over the last two decades, genes have been identified whose expression is induced by desiccation in diverse, desiccation-tolerant (DT) taxa, including, e.g., late embryogenesis abundant proteins (LEA) and reactive oxygen species scavengers. This up-regulation is observed in DT resurrection plants, mosses, and green algae most closely related to these Embryophytes. Here we test whether this same suite of protective genes is up-regulated during desiccation in even more distantly related DT green algae, and, importantly, whether that up-regulation is unique to DT algae or also occurs in a desiccation-intolerant relative. We used three closely related aquatic and desert-derived green microalgae in the family Scenedesmaceae and capitalized on extraordinary desiccation tolerance in two of the species, contrasting with desiccation intolerance in the third. We found that during desiccation, all three species increased expression of common protective genes. The feature distinguishing gene expression in DT algae, however, was extensive down-regulation of gene expression associated with diverse metabolic processes during the desiccation time course, suggesting a switch from active growth to energy-saving metabolism. This widespread downshift did not occur in the desiccation-intolerant taxon. These results show that desiccation-induced up-regulation of expression of protective genes may be necessary but is not sufficient to confer desiccation tolerance. The data also suggest that desiccation tolerance may require induced protective mechanisms operating in concert with massive down-regulation of gene expression controlling numerous other aspects of metabolism.

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Desiccation Tolerance as the Basis of Long-Term Seed Viability

International Journal of Molecular Sciences ◽

10.3390/ijms22010101 ◽

2020 ◽

Vol 22 (1) ◽

pp. 101

Author(s):

Galina Smolikova ◽

Tatiana Leonova ◽

Natalia Vashurina ◽

Andrej Frolov ◽

Sergei Medvedev

Keyword(s):

Desiccation Tolerance ◽

Vascular Plants ◽

Molecular Mechanisms ◽

Regulation Of Gene Expression ◽

Seed Viability ◽

Late Embryogenesis Abundant ◽

Maturation Stage ◽

Terrestrial Plants ◽

Complex Anatomy ◽

Orthodox Seeds

Desiccation tolerance appeared as the key adaptation feature of photoautotrophic organisms for survival in terrestrial habitats. During the further evolution, vascular plants developed complex anatomy structures and molecular mechanisms to maintain the hydrated state of cell environment and sustain dehydration. However, the role of the genes encoding the mechanisms behind this adaptive feature of terrestrial plants changed with their evolution. Thus, in higher vascular plants it is restricted to protection of spores, seeds and pollen from dehydration, whereas the mature vegetative stages became sensitive to desiccation. During maturation, orthodox seeds lose up to 95% of water and successfully enter dormancy. This feature allows seeds maintaining their viability even under strongly fluctuating environmental conditions. The mechanisms behind the desiccation tolerance are activated at the late seed maturation stage and are associated with the accumulation of late embryogenesis abundant (LEA) proteins, small heat shock proteins (sHSP), non-reducing oligosaccharides, and antioxidants of different chemical nature. The main regulators of maturation and desiccation tolerance are abscisic acid and protein DOG1, which control the network of transcription factors, represented by LEC1, LEC2, FUS3, ABI3, ABI5, AGL67, PLATZ1, PLATZ2. This network is complemented by epigenetic regulation of gene expression via methylation of DNA, post-translational modifications of histones and chromatin remodeling. These fine regulatory mechanisms allow orthodox seeds maintaining desiccation tolerance during the whole period of germination up to the stage of radicle protrusion. This time point, in which seeds lose desiccation tolerance, is critical for the whole process of seed development.

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Translational down-regulation of gene expression

Pathophysiology ◽

10.1016/s0928-4680(98)80759-1 ◽

1998 ◽

Vol 5 ◽

pp. 122

Author(s):

D.B. Thomason ◽

J. Wong ◽

L. Fu ◽

E. Schneider ◽

Z. Ku ◽

...

Keyword(s):

Gene Expression ◽

Regulation Of Gene Expression ◽

Down Regulation

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Lack of Obvious Influence of PLLA Nanofibers on the Gene Expression of BMP-2 and VEGF during Growth and Differentiation of Human Mesenchymal Stem Cells

The Scientific World JOURNAL ◽

10.1100/tsw.2009.36 ◽

2009 ◽

Vol 9 ◽

pp. 313-319 ◽

Cited By ~ 4

Author(s):

Markus D. Schofer ◽

S. Fuchs-Winkelmann ◽

C. Wack ◽

M. Rudisile ◽

R. Dersch ◽

...

Keyword(s):

Gene Expression ◽

Growth Factor ◽

Time Course ◽

Negative Impact ◽

Fracture Repair ◽

Bone Morphogenetic Protein 2 ◽

Vegf Gene ◽

Down Regulation ◽

Artificial Graft ◽

The Impact

Growth factors like bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF) play an important role in bone remodeling and fracture repair. Therefore, with respect to tissue engineering, an artificial graft should have no negative impact on the expression of these factors. In this context, the aim of this study was to analyze the impact of poly(L-lactic acid) (PLLA) nanofibers on VEGF and BMP-2 gene expression during the time course of human mesenchymal stem cell (hMSC) differentiation towards osteoblasts. PLLA matrices were seeded with hMSCs and cultivated over a period of 22 days under growth and osteoinductive conditions, and analyzed during the course of culture, with respect to gene expression of VEGF and BMP-2. Furthermore, BMP-2–enwoven PLLA nanofibers were used in order to elucidate whether initial down-regulation of growth factor expression could be compensated. Although there was a great interpatient variability with respect to the expression of VEGF and BMP-2, PLLA nanofibers tend to result in a down-regulation in BMP-2 expression during the early phase of cultivation. This effect was diminished in the case of VEGF gene expression. The initial down-regulation was overcome when BMP-2 was directly incorporated into the PLLA nanofibers by electrospinning. Furthermore, the incorporation of BMP-2 into the PLLA nanofibers resulted in an increase in VEGF gene expression. Summarized, the results indicate that the PLLA nanofibers have little effect on growth factor production. An enhancement in gene expression of BMP-2 and VEGF can be achieved by an incorporation of BMP-2 into the PLLA nanofibers.

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Comparisons of the effects of tamoxifen, toremifene and raloxifene on enzyme induction and gene expression in the ovariectomised rat uterus

Journal of Endocrinology ◽

10.1677/joe.0.1700555 ◽

2001 ◽

Vol 170 (3) ◽

pp. 555-564 ◽

Cited By ~ 11

Author(s):

AR Green ◽

EL Parrott ◽

M Butterworth ◽

PS Jones ◽

P Greaves ◽

...

Keyword(s):

Gene Expression ◽

Time Course ◽

Rt Pcr ◽

Biphasic Response ◽

Down Regulation ◽

Rat Uterus ◽

Carcinogenic Effects ◽

The Difference ◽

Er Alpha ◽

Ovariectomised Rats

This study compares the actions of oestradiol, tamoxifen, toremifene and raloxifene on enzyme and gene expression in uterine tissues of ovariectomised rats over 72 h. The time-course for the induction of ornithine decarboxylase by the compounds showed a rapid biphasic response, while for creatine kinase brain type (BB) there was a continued increase over 72 h. The efficacy of induction showed that, with both markers, oestradiol gave the highest induction level, followed by tamoxifen or toremifene and then raloxifene. RT-PCR demonstrated that all compounds decreased oestrogen receptor (ER) alpha, ERbeta and ERbeta2 gene expression, 8-24 h after the first dose, suggesting that down-regulation of ER is not the primary cause of the difference in efficacy between these compounds. Using cDNA arrays, expression of 512 genes was examined in the uteri of oestradiol- or tamoxifen-treated rats. Both compounds resulted in the up-regulation of heat-shock protein 27, telomerase-associated protein 1 and secretin. However, most surprising was the marked down-regulation of Wilms' tumour and retinoblastoma genes. We speculate that this may result in a loss of regulation of the transition from the G1 to the S phase in the cell cycle and may make cells more vulnerable to the carcinogenic effects of tamoxifen in this tissue.

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Regulation of the Discoidin I gamma gene in Dictyostelium discoideum: identification of individual promoter elements mediating induction of transcription and repression by cyclic AMP

Molecular and Cellular Biology ◽

10.1128/mcb.10.8.4080-4088.1990 ◽

1990 ◽

Vol 10 (8) ◽

pp. 4080-4088

Author(s):

F Vauti ◽

P Morandini ◽

J Blusch ◽

A Sachse ◽

W Nellen

Keyword(s):

Gene Expression ◽

Cyclic Amp ◽

Dictyostelium Discoideum ◽

Base Pair ◽

Regulation Of Gene Expression ◽

Promoter Elements ◽

Down Regulation ◽

Heterologous Promoter ◽

Sequence Element ◽

Pair Sequence

We dissected the promoter of the developmentally induced and cyclic AMP-repressed discoidin I gamma gene and identified a sequence element essential for developmental induction. Transfer of the element to an inactive heterologous promoter demonstrated that this sequence is sufficient to confer expression in axenically growing cells and to induce gene activity in development after growth on bacteria. A 16-base-pair sequence within this element was shown to be sufficient for induction in the discoidin promoter context and was used to reactivate different truncated promoter constructs. This led to the localization of an element necessary for down regulation of gene expression by extracellular cyclic AMP.

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