Modulation of the polyamine biosynthetic pathway in transgenic rice confers tolerance to drought stress

Abstract

We have generated transgenic rice plants expressing the Datura stramonium adc gene and investigated their response to drought stress. We monitored the steady-state mRNA levels of genes involved in polyamine biosynthesis (Datura adc, rice adc, and rice samdc) and polyamine levels. Wild-type plants responded to the onset of drought stress by increasing endogenous putrescine levels, but this was insufficient to trigger the conversion of putrescine into spermidine and spermine (the agents that are believed to protect plants under stress). In contrast, transgenic plants expressing Datura adc produced much higher levels of putrescine under stress, promoting spermidine and spermine synthesis and ultimately protecting the plants from drought. We demonstrate clearly that the manipulation of polyamine biosynthesis in plants can produce drought-tolerant germplasm, and we propose a model consistent with the role of polyamines in the protection of plants against abiotic stress.A biotic stresses such as drought represent some of the most significant constraints to agricultural productivity. Transgenic approaches can be used in combination with conventional breeding strategies to create crops with enhanced drought tolerance, and one way in which this can be achieved is through the manipulation of polyamine metabolism. Polyamines are small, ubiquitous, nitrogenous compounds that have been implicated in a variety of stress responses in plants (1). The link between polyamines and abiotic stress was first documented through putrescine accumulation in response to suboptimal potassium levels in barley (2). Since then, a connection has been suggested between increased putrescine levels and abiotic stress (3). Similar phenomena have been described in animals, e.g., during ischemic and postischemic responses in neurons (4). The physiological role of putrescine in abiotic stress responses is a matter of controversy. It has been very difficult to establish a direct cause-and-effect relationship between increased putrescine levels in plants and abiotic stress. Elevated putrescine might be the cause of stress-induced injury or, alternatively, a protective response resulting from stress (5).The genetic manipulation of polyamine metabolism has become a valuable tool for studying their physiological roles in plants (6). Plant polyamine content has been modulated by the overexpression͞down-regulation of arginine decarboxylase (adc), ornithine decarboxylase (odc), and S-adenosylmethionine decarboxylase (samdc) (6-10). Overexpression of heterologous adc or odc cDNAs in plants generally results in the production of high levels of putrescine (11-13). In most cases, this is accompanied by a relatively small increase in spermidine and spermine concentrations (7,14). Such findings suggest that the levels of spermidine and spermine are under strict homeostatic regulation (15). Therefore, the study of plants transformed with genes involved in polyamine biosynthesis may shed light on the importance of polyamines, their role in the acquisition of stress ...

The mutual responses of higher plants to environment: Physiological and microbiological aspects

“…Previous gene engineering strategy for plant stress resistance was to express one (in most cases) or several stress-tolerant genes by constitutive or stress-induced promoters [19]. For instance, by introducing betA gene derived from E. coli into tobacco and potato, betaine content in the transgenic plants increased to 5 mol/g (dry weight) and tolerance to salt and cold for the transgenic plants was improved greatly.…”

“…Physiological and microbiological responses of higher plants to environment have been studied extensively over the world, especially by targeting model plants and crop plants [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Abiotic stresses in environment are linked with all the living process of higher plants and greatly influence plant productivity developmental cues and environmental stimuli, most of which are the important factors affecting eco-environment such as low temperature, drought, salinity and UV-B radiation, which often occur in terrestrial ecosystem.…”

“…In practice, the key point to agriculture is how to regulate the harmonious relationship between soil-environment and crops and make the best of physiological potential of crops [137][138][139][140][141][142][143][144][145][146][147]. So, adaptation in plants is an important topic in basic and applied biology under global climate change [11,[15][16][17][18][19][43][44][45][46][47][48][104][105][106][107]120]. In the discipline context, it is very interesting to understand the interaction between plants and their environment.…”

Increased Polyamine Biosynthesis Enhances Stress Tolerance by Preventing the Accumulation of Reactive Oxygen Species: T-DNA Mutational Analysis of Oryza sativa Lysine Decarboxylase-like Protein 1

“…It was recently suggested that there is a reverse PA pathway in plants from spermine to putrescine (Kusano et al, 2008). The biosynthetic pathway that converts putrescine into spermidine and spermine is also important in conferring plant stress tolerance (Capell et al, 2004). …”

BUD2, encoding an S-adenosylmethionine decarboxylase, is required for Arabidopsis growth and development

“…At the cellular level, polyamines are organic cations, interacting with the macromolecules that possess anionic groups such as DNA, RNA, lipids and proteins, thereby influencing DNA conformation, gene expression and protein synthesis, and modulating enzyme activity. In higher plants, polyamines are able to affect membrane fluidity by binding to phospholipids in membrane [4] and mediate biotic and abiotic stress responses, such as pathogen infection, osmotic stress, potassium deficiency and wounding [5][6][7][8][9]. Previous observations revealed that polyamines may be involved in a variety of plant developmental processes, such as cell division, root initiation, somatic embryogenesis, xylogenesis, flower development, fruit ripening and senescence [3].…”