Department of Entomology and Plant Pathology, Auburn University, Auburn, Alabama, USA; email:
Department of Biological Sciences, Auburn University, Auburn, Alabama, USA.
Annu Rev Phytopathol. 2022 Aug 26;60:163-186. doi: 10.1146/annurev-phyto-021021-041716. Epub 2022 Apr 26.
A group of aggressive pathogens have evolved to colonize the plant xylem. In this vascular tissue, where water and nutrients are transported from the roots to the rest of the plant, pathogens must be able to thrive under acropetal xylem sap flow and scarcity of nutrients while having direct contact only with predominantly dead cells. Nevertheless, a few bacteria have adapted to exclusively live in the xylem, and various pathogens may colonize other plant niches without causing symptoms unless they reach the xylem. Once established, the pathogens modulate its physicochemical conditions to enhance their growth and virulence. Adaptation to the restrictive lifestyle of the xylem leads to genome reduction in xylem-restricted bacteria, as they have a higher proportion of pseudogenes in their genome. The basis of xylem adaptation is not completely understood; therefore, a need still exists for model systems to advance the knowledge on this topic.
一组侵袭性病原体已进化为定殖于植物木质部。在这个维管束组织中，水和养分从根部输送到植物的其余部分，病原体必须能够在向顶木质部汁液流动和养分稀缺的情况下茁壮成长，同时仅与主要是死细胞直接接触。然而，有一些细菌已经适应了专门生活在木质部中，而且各种病原体可能会在不引起症状的情况下定植于其他植物小生境，除非它们到达木质部。一旦建立，病原体就会调节其物理化学条件，以促进其生长和毒力。对木质部限制生活方式的适应导致木质部限制细菌的基因组减少，因为它们的基因组中有更高比例的假基因。木质部适应的基础尚不完全清楚；因此，仍然需要模型系统来推进这一主题的知识。
