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پاسخهای گیاه– قارچ میکوریز به تنش خشکی: واکاوی فرآیندهای زیستی و سازوکارهای دفاعی | ||
| زیست شناسی خاک | ||
| مقالات آماده انتشار، پذیرفته شده، انتشار آنلاین از تاریخ 05 اسفند 1404 | ||
| نوع مقاله: مقاله مروری | ||
| شناسه دیجیتال (DOI): 10.22092/sbj.2026.371633.290 | ||
| نویسنده | ||
| حبیب اله نادیان قمشه* | ||
| (بازنشسته) گروه خاکشناسی-دانشگاه کشاورزی و منابع طبیعی رامین خوزستان | ||
| چکیده | ||
| تنش خشکی یکی از مهمترین چالشهای کشاورزی در مناطق خشک و نیمهخشک است که سبب آسیبهای فراوان از جمله صدمات اکسیداتیو در گیاهان میشود. تحت تنش خشکی، بسیاری از فرایندهای زیستی گیاه عمدتا به سبب انباشت گونههای فعال اکسیژن مختل میشود. سازوکارهای متنوع دفاع آنتیاکسیدانی، گیاهان را قادر میسازد تا ضمن مقابله با تنش اکسیداتیو، توازن ردوکس و همستازی گونههای فعال اکسیژن را در شرایط تنش تا حدودی حفظ کنند. آنزیمهای آنتیاکسیدان کلیدی مانند سوپراکسید دیسموتاز و کاتالاز نقش بسیار مهمی در خنثی کردن گونههای فعال اکسیژن دارند، حال آنکه آنتیاکسیدانهای غیر آنزیمی بیشتر از طریق مهار و دفع گونههای فعال اکسیژن در کاهش تنش اکسیداتیو شرکت میکنند. سازوکارهای دفاعی گیاهان در همزیستی با قارچهای میکوریز آربسکولار در مقابله با تنش خشکی به صورت همافزایی مشاهده میشود. قارچهای میکوریز علاوه بر فعالیتهای آنتیاکسیدانی خود از طریق طیف وسیعی از متابولیتها، قادرند با تنظیمات اسمزی، بیان ژنهای کلیدی پاسخدهنده به خشکی و نیز بهبود تغذیه گیاه آسیبهای ناشی از تنش خشکی در گیاه میزبان خود را کاهش دهند. هر چند پیشرفتهای اخیر با استفاده از زیستشناسی مولکولی و مهندسی ژنتیک تا حدودی توانسته است چگونگی سیگنالدهی گونههای فعال اکسیژن و سیستمهای آنتیاکسیدانهای آنزیمی و غیر آنزیمی و نیز برهمکنشهای پیچیده هورمونی در پاسخ به تنش خشکی را روشن کنند، ولی هنوز بسیاری از این سازوکارها ناشناخته باقی مانده است. بدون شک پژوهشهای آینده با تمرکز بر زوایای ناشناخته و پنهان تنظیمکنندههای اصلی پاسخهای فیزیولوژیک و بیوشیمیایی گیاه در برابر تنش خشکی میتوانند به توسعه کشاورزی پایدار و مقاوم به خشکی کمک کنند | ||
| کلیدواژهها | ||
| آنتی اکسیدانهای آنزیمی و غیر آنزیمی؛ پراکسید هیدرژن؛ پرولین؛ تنش خشکی؛ قارچهای میکوریزا | ||
| عنوان مقاله [English] | ||
| Plant-mycorrhiza responses to drought stress: Analysis of vital processes and defense mechanisms | ||
| نویسندگان [English] | ||
| Habiballah Nadian Ghomsheh | ||
| Professor emeritus | ||
| چکیده [English] | ||
| Plant-mycorrhiza responses to drought stress: Analysis of vital processes and defense mechanisms Background and Objectives: Drought stress is one of the most critical challenges in agriculture, especially in arid and semi-arid regions. In light of ongoing climate change and prolonged drought periods, this issue has posed a serious threat to food security, particularly in countries located in Western Asia. Drought stress severely affects many physiological, enzymatic, biochemical, and nutritional processes in plants. Among the most important physiological and biochemical effects of drought stress are disturbances in photosynthesis and the photosynthetic electron transport chain, intercellular CO₂ concentration, photosynthetic rate, stomatal conductance, transpiration rate, excessive production of reactive oxygen species (ROS), disruptions in plant water potential, and alterations in the regulation and synthesis of enzymatic, non-enzymatic, and hormonal osmolytes. To cope with the damage caused by drought stress, plants—alongside appropriate morphological adjustments activate a set of protective mechanisms (such as increased synthesis of antioxidant metabolites) and regulatory mechanisms (such as enhancing osmotic regulators) in conjunction with molecular responses. In fact, upon perceiving stress signals through the roots, the plant increases the expression of regulatory protein genes such as calcium-dependent protein kinases and mitogen-activated protein kinases, as well as the expression of genes involved in the synthesis of osmolytes including proline, glycine betaine, LEA proteins, and soluble sugars. These responses not only mitigate oxidative stress but also help improve plant water relations. The defensive mechanisms of plants in symbiosis with arbuscular mycorrhizal fungi are activated synergistically to counteract drought stress. Review Methods: Numerous studies have highlighted the pivotal role of soil organisms, particularly arbuscular mycorrhizal fungi, in alleviating the detrimental effects of drought stress and mediating the shared defense mechanisms between plants and fungi. These investigations encompass a wide range of plant responses under drought conditions, both in the presence and absence of mycorrhizal associations, and are derived from peer-reviewed journals and reputable scientific databases. This analytical review synthesizes the findings of researchers in the field, drawing on up-to-date studies on drought stress physiology, antioxidant metabolism, osmolyte accumulation, and molecular responses, accessed through major international databases including Web of Science and Scopus. Furthermore, Google Scholar provided a freely accessible platform for identifying recent publications, while specialized resources such as ScienceDirect, SpringerLink and Taylor & Francis offered valuable journal articles, book chapters, and authoritative reference works in the fields of mycorrhizal symbiosis and soil ecology. Results: Under drought stress, plant water relations are disrupted due to a reduction in the moisture potential gradient between the soil solution and plant tissues. Stomatal closure, aimed at reducing water loss, is one of the plant’s earliest responses to drought conditions. This stress not only impairs photosynthetic processes but also leads to excessive production and accumulation of reactive oxygen species (ROS), resulting in oxidative damage at the cellular level. To cope with the damaging effects of drought stress, plants along with appropriate morphological adjustments activate a series of protective mechanisms (such as enhanced synthesis of antioxidant metabolites), regulatory mechanisms (such as increased osmotic adjustment), and molecular responses. Numerous studies have shown that mycorrhizal fungi can participate in these protective and regulatory mechanisms, thereby enhancing the host plant’s adaptive capacity through various pathways. Mycorrhizal colonization supports the plant by promoting the synthesis and accumulation of osmotic regulators and antioxidant compounds, thus providing effective protection under drought conditions. A reduction in osmotic metabolites is considered a drought avoidance mechanism, whereas increased accumulation of osmotic regulators and antioxidant compounds represents a drought tolerance strategy. In the interaction between mycorrhizal fungi and aquaporins in reducing drought stress in the host plant, several mechanisms are involved. Among these mechanisms is the upregulation or stabilization of key aquaporin genes such as PIP1;6, PIP2;1, and PIP2;5. Gene expression regulation—particularly when mediated by mycorrhizal fungi—constitutes one of the earliest and most important mechanisms enabling drought tolerance. The interaction between aquaporins and stomata under drought conditions is coordinated by mycorrhizal fungi in a manner that ensures optimal water relations depending on the intensity of the drought and the plant’s sensitivity to it. Upon sensing drought stress through their root system, plants transmit signals to various organs to adjust cellular processes accordingly. One such response is the synthesis of osmolytes such as proline, glycine betaine, and LEA proteins, which contribute to physiological, biochemical, and molecular adjustments that improve osmotic potential, enhance water relations, maintain cellular homeostasis, and ultimately increase drought tolerance—particularly in the presence of mycorrhizal fungi. Additionally, mycorrhizal plants exhibit enhanced synthesis of enzymatic antioxidants such as superoxide dismutase (SOD) and catalase (CAT), as well as antioxidant-related phytohormones including gibberellic acids, abscisic acid (ABA), indole-3-acetic acid (IAA), and jasmonic acid (JA). These compounds, each with distinct and sometimes contrasting physiological roles, act in a coordinated and synergistic manner to substantially mitigate the detrimental effects of drought stress on plant growth, nutrition, and physiological performance. Conclusion: Plants employ complex antioxidant defense systems to mitigate the damaging effects of drought stress, relying on both enzymatic and non-enzymatic metabolites. Arbuscular mycorrhizal fungi substantially strengthen these defenses by enhancing ROS scavenging, stabilizing photosynthetic and redox processes, and improving osmotic adjustment, nutrient uptake, and the expression of drought-responsive genes. This symbiosis effectively contributes to ROS homeostasis and reduces oxidative damage, thereby improving plant resilience under water-limited conditions. Despite recent advances in molecular biology that have clarified elements of ROS signaling, antioxidant pathways, and hormonal crosstalk, many aspects of plant–mycorrhiza interactions under drought remain unresolved. Continued research using modern biotechnological approaches is essential for uncovering these mechanisms and developing more drought-tolerant crops that can support future global food security. | ||
| کلیدواژهها [English] | ||
| drought stress, enzymatic and non-enzymatic antioxidants, mycorrhizal fungi, Hydrogen peroxide, Proline | ||
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