دانلود رایگان ترجمه مقاله واکنش های ترکیبی ریشه برای مقابله با کمبود فسفر – Academic Journals 2008
دانلود رایگان مقاله انگلیسی نقل و انتقال ساکارز در آوند: واکنش های ترکیبی ریشه برای مقابله با کمبود فسفر به همراه ترجمه فارسی
عنوان فارسی مقاله: | نقل و انتقال ساکارز در آوند: واکنش های ترکیبی ریشه برای مقابله با کمبود فسفر |
عنوان انگلیسی مقاله: | Sucrose transport in the phloem: integrating root responses to phosphorus starvation |
رشته های مرتبط: | زیست شناسی، کشاورزی، علوم باغبانی، علوم گیاهی، فیزیولوژی گیاهی، ژنتیک و علوم سلولی و مولکولی |
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نشریه | Academic Journals |
کد محصول | f196 |
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بخشی از ترجمه فارسی مقاله: تعریف نقش ساکارز در فرستادن سیگنال |
بخشی از مقاله انگلیسی: Defining sucrose as a signal The purpose of this review is to explore the potential for shoot-derived carbohydrate signals to initiate acclimatory responses in roots to phosphorus (P) starvation. In this context, these carbohydrates act as systemic plant growth regulators. For shoot-derived carbohydrates to act as causal intermediary signals in co-ordinating root responses to P starvation they must meet the following criteria (sensu White, 2000): (i) root physiological and biochemical responses must be preceded by an increase in the biosynthesis of shoot carbohydrates and their translocation via the phloem to the root, (ii) blocking the biosynthesis or translocation of shoot carbohydrates must eliminate, or attenuate, the root physiological and biochemical responses to P starvation, and (iii) artificial changes in carbohydrate concentrations in the root, similar to those experienced in P-starved plants, must initiate similar responses to those induced by P starvation. This review will test each criterion and establish the potential for shoot-derived carbohydrates to act as systemic signals coordinating root responses to P starvation. Whilst exploring these criteria the mechanism by which sucrose might act as a signal will also be considered. For example, is there a change in phloem sucrose concentration or is there increased phloem flux to the roots? Is any change in phloem sucrose transient or sustained throughout P starvation? Is any change reversed on re-supply of P or is a further signal required? Although it may not be possible to answer all these questions, they will serve as a focus for future research into phloem sucrose and its ability to co-ordinate root responses to P starvation. Sensing and signalling P availability Phosphorus is the second most limiting mineral nutrient in crop production after nitrogen (Vance et al., 2003). It is thought that a mechanistic understanding of how plants sense and respond to P starvation might facilitate selection, breeding, and GM approaches to improve crop production, and reduce our reliance on non-renewable inorganic P fertilizers (Vance et al., 2003; Hammond et al., 2004; Jain et al., 2007b). This may ultimately lower production costs, our reliance on mineral fertilizers, and P pollution to surface and groundwaters (Hammond et al., 2004). Phosphorus starvation in plants initiates a myriad of transcriptional, biochemical, and physiological responses that serve either to enhance the plant’s ability to acquire P from the soil or improve the efficiency with which plants utilize P internally (Fig. 1; Vance et al., 2003; FrancoZorrilla et al., 2004; Hammond et al., 2004; Jain et al., 2007b). Our knowledge of how plants sense their P status and initiate responses to P starvation is increasing rapidly, although much still remains to be discovered. It is probable that plants can detect both whole plant P status, enabling efficient use of P internally, and local variations in P availability, enabling the proliferation of roots in P-rich patches (Fig. 1; Forde and Lorenzo, 2001; Williamson et al., 2001; Amtmann et al., 2006). A complex series of signalling cascades is emerging that control plant responses to P starvation. These include many transcription factors. The first transcription factor implicated in regulating plant P starvation responses was PHR1, a myb transcription factor (Rubio et al., 2001). The PHR1 protein was shown to bind to an imperfectpalindromic sequence (P1BS; GNATATNC), which is present in the promoter regions of many P starvationinduced genes (Rubio et al., 2001; Hammond et al., 2004). The expression of PHR1 appears to be constitutive, irrespective of plant P status, however, recent evidence suggests that the PHR1 protein may be targeted by a small ubiquitin-like modifier (SUMO) E3 ligase (SIZ1), whose expression is increased by P starvation (Miura et al., 2005). Sumoylation appears to modify the function of proteins in distinct ways; by altering their cellular location, activity, stability, or susceptibility to degradation by ubiquitination (Mu¨ller et al., 2001; Johnson, 2004; Kerscher et al., 2006). Interestingly, the Arabidopsis siz1 knockout mutant is hypersensitive to P starvation, suggesting SIZ1 acts as a repressor of plant responses to P starvation. Arabidopsis siz1 maintains many characteristic phenotypic responses to P starvation, including reduced primary root growth and increased lateral root and root hair number and length, increased root:shoot ratio, and increased anthocyanin accumulation (Miura et al., 2005). Interestingly, the expression of three P starvation-responsive genes, AtPT2, AtPS2, and AtPS3 are greater in siz1 compared with wild-type plants under P-replete conditions, and still show increases in expression during P starvation. However, the transcript accumulation of two other P-responsive genes, AtIPS1 and AtRNS1, occurs at a reduced rate in siz1 seedlings compared with wild-type seedlings, despite the presence of the P1BS sequence in their promoter regions (Miura et al., 2005). |