Seifi Hamed, De Vleesschauwer David, Aziz Aziz, Höfte Monica
Laboratory of Phytopathology; Department of Crop Protection; Faculty of Bioscience Engineering; Ghent University; Ghent, Belgium.
Laboratory of SDRP-URVVC EA 4707; University of Reims; Campus Moulin de la Housse; Cedex 2, France.
Plant Signal Behav. 2014;9(2):e27995. doi: 10.4161/psb.27995. Epub 2014 Feb 12.
The fungal plant pathogen Botrytis cinerea is the causal agent of the "gray mold" disease on a broad range of hosts. As an archetypal necrotroph, B. cinerea has evolved multiple virulence strategies for inducing cell death in its host. Moreover, progress of B. cinerea colonization is commonly associated with induction of senescence in the host tissue, even in non-invaded regions. In a recent study, we showed that abscisic acid deficiency in the sitiens tomato mutant culminates in an anti-senescence defense mechanism which effectively contributes to resistance against B. cinerea infection. Conversely, in susceptible wild-type tomato a strong induction of senescence could be observed following B. cinerea infection. Building upon this earlier work, we here discuss the immune-regulatory role of a key senescence-associated protein, asparagine synthetase. We found that infection of wild-type tomato leads to a strong transcriptional upregulation of asparagine synthetase, followed by a severe depletion of asparagine titers. In contrast, resistant sitiens plants displayed a strong induction of asparagine throughout the course of infection. We hypothesize that rapid activation of asparagine synthetase in susceptible tomato may play a dual role in promoting Botrytis cinerea pathogenesis by providing a rich source of N for the pathogen, on the one hand, and facilitating pathogen-induced host senescence, on the other.
真菌植物病原菌灰葡萄孢是多种寄主上“灰霉病”的致病因子。作为一种典型的死体营养型病原菌，灰葡萄孢已进化出多种致病策略来诱导寄主细胞死亡。此外，灰葡萄孢的定殖过程通常与寄主组织中衰老的诱导有关，即使在未侵染区域也是如此。在最近的一项研究中，我们发现番茄突变体sitiens中脱落酸缺乏最终导致一种抗衰老防御机制，该机制有效地促进了对灰葡萄孢感染的抗性。相反，在易感的野生型番茄中，灰葡萄孢感染后可观察到强烈的衰老诱导。基于早期的这项工作，我们在此讨论一种关键的衰老相关蛋白——天冬酰胺合成酶的免疫调节作用。我们发现野生型番茄感染后会导致天冬酰胺合成酶的转录强烈上调，随后天冬酰胺水平严重降低。相比之下，抗性sitiens植株在整个感染过程中都表现出天冬酰胺的强烈诱导。我们推测，易感番茄中天冬酰胺合成酶的快速激活可能在促进灰葡萄孢致病方面发挥双重作用，一方面为病原菌提供丰富的氮源，另一方面促进病原菌诱导的寄主衰老。
