Moret Florian, Jacquens Lucile, Larignon Philippe, Clément Gilles, Coppin Cindy, Noirot Elodie, Courty Pierre-Emmanuel, Fontaine Florence, Adrian Marielle, Trouvelot Sophie
Agroécologie, INRAE, Institut Agro, Univ. Bourgogne, Dijon, France.
IFV, Pôle Rhône-Méditerranée, Rodilhan, France.
Front Plant Sci. 2024 Apr 23;15:1394821. doi: 10.3389/fpls.2024.1394821. eCollection 2024.
Botryosphaeria dieback is a grapevine trunk disease caused by fungi of the Botryosphaeriaceae family, which attacks more specifically the woody tissues. The infection leads to different symptoms including a severe form with a leaf drop as well as premature plant death. Botryosphaeria dieback causes major economic losses, since no effective treatment is yet available. A better understanding is necessary to find solutions to fight this disease. In this study, our objective was to characterize the "leaf drop" form by (1) looking for the presence of pathogens in the basal internodes of stems, (2) quantifying blocked vessels by tylosis and/or gummosis, and (3) describing the impact of the disease on vine physiology (gene expression and metabolome) and development (establishment and functioning of the cambium and phellogen) at the level of xylem and phloem of basal stem internodes. Our study has shown that Botryosphaeriaceae were present in both phloem and xylem of the basal internodes of the annual stem, with xylem vessels obturated. We have also clearly demonstrated that gene expression and metabolite profiles were strongly modified in both xylem and phloem of diseased plants. Differences in stems between healthy (control, C) and diseased (D) plants were low at flowering (vines not yet symptomatic), higher at the onset of symptom expression and still present, although less marked, at full disease expression. qRT-PCR analysis showed in both phloem and xylem an overexpression of genes involved in plant defense, and a repression of genes related to meristematic activity (i.e. vascular cambium and phellogen). Metabolomic analysis showed specific fingerprints in stems of healthy and diseased plants from the onset of symptom expression, with an increase of the level of phytoalexins and mannitol, and a decrease of 1-kestose one. At the structural level, many alterations were observed in internodes, even before the onset of symptoms: a classical obstruction of xylem vessels and, for the first time, a disorganization of the secondary phloem with an obstruction of the sieve plates by callose. The disease modifies the development of both secondary phloem (liber) and phellogen. Altogether, this study combining different approaches allowed to highlight deep vine dysfunction in the internodes at the base of stems, that may explain vine decline due to Botryosphaeria dieback.
葡萄座腔菌溃疡病是一种由葡萄座腔菌科真菌引起的葡萄树干病害，该病害主要侵袭木质组织。感染会导致不同症状，包括严重形式的落叶以及植株过早死亡。由于目前尚无有效治疗方法，葡萄座腔菌溃疡病造成了重大经济损失。有必要深入了解该病以找到防治方法。在本研究中，我们的目标是通过以下方式对“落叶”形式进行特征描述：（1）查找茎基部节间中病原体的存在情况；（2）量化由侵填体和/或树胶形成导致的导管堵塞情况；（3）描述该病害在茎基部节间木质部和韧皮部水平上对葡萄生理（基因表达和代谢组）和发育（形成层和木栓形成层的建立及功能）的影响。我们的研究表明，葡萄座腔菌科真菌存在于一年生茎基部节间的韧皮部和木质部中，木质部导管堵塞。我们还清楚地证明，患病植株的木质部和韧皮部中的基因表达和代谢物谱均发生了强烈改变。健康（对照，C）植株和患病（D）植株的茎在开花期（葡萄尚未出现症状）差异较小，在症状开始出现时差异较大，并且在病害完全显现时差异仍然存在，尽管不太明显。定量逆转录聚合酶链反应（qRT-PCR）分析表明，韧皮部和木质部中参与植物防御的基因均过度表达，而与分生组织活性（即维管形成层和木栓形成层）相关的基因受到抑制。代谢组学分析表明，从症状开始出现起，健康和患病植株的茎中就有特定的指纹图谱，植保素和甘露醇水平升高，而蔗果三糖水平降低。在结构层面，甚至在症状出现之前，节间就观察到了许多变化：木质部导管出现典型堵塞，并且首次发现次生韧皮部紊乱，胼胝质堵塞筛板。该病害改变了次生韧皮部（韧皮部）和木栓形成层的发育。总之，本研究综合运用不同方法，突出了茎基部节间葡萄的深层功能障碍，这可能解释了由葡萄座腔菌溃疡病导致的葡萄衰退现象。
