Sarkar Poulami, Jassar Ola, Ghanim Murad
Department of Entomology, Volcani Institute, Rishon LeZion, Israel.
Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel.
Microbiol Spectr. 2023 Sep 28;11(5):e0130123. doi: 10.1128/spectrum.01301-23.
Autophagy plays an important role against pathogen infection in many organisms; however, little has been done with regard to vector-borne plant and animal pathogens, that sometimes replicate and cause deleterious effects in their vectors. Liberibacter solanacearum (CLso) is a fastidious gram-negative phloem-restricted plant pathogen and vectored by the carrot psyllid, . The plant disease caused by this bacterium is called carrot yellows and has recently gained much importance due to worldwide excessive economical losses. Here, we demonstrate that calcium ATPase, cytosolic calcium, and most importantly Beclin-1 have a role in regulating autophagy and its association with Liberibacter inside the psyllid. The presence of CLso generates reactive oxygen species and induces the expression of detoxification enzymes in the psyllid midguts, a main site for bacteria transmission. CLso also induces the expression of both sarco/endoplasmic reticulum Ca2+pump (SERCA) and 1,4,5-trisphosphate receptors (ITPR) in midguts, resulting in high levels of calcium in the cellular cytosol. Silencing these genes individually disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and subsequently on Liberibacter persistence and transmission. Inhibiting Beclin1-phosphorylation through different calcium-induced kinases altered the expression of autophagy and CLso titers and persistence. Based on our results obtained from the midgut, we suggest the existence of a direct correlation between cytosolic calcium levels, autophagy, and CLso persistence and transmission by the carrot psyllid. IMPORTANCE Plant diseases caused by vector-borne Liberibacter species are responsible for the most important economic losses in many agricultural sectors. Preventing these diseases relies mostly on chemical sprays against the insect vectors. Knowledge-based interference with the bacteria-vector interaction remains a promising approach as a sustainable solution. For unravelling how Liberibacter exploits molecular pathways in its insect vector for transmission, here, we show that the bacterium manipulates calcium levels on both sides of the endoplasmic reticulum membrane, resulting in manipulating autophagy. Silencing genes associated with these pathways disrupted the calcium levels in the cytosol and resulted in direct effects on autophagy and Liberibacter transmission. These results demonstrate major pathways that could be exploited for manipulating and controlling the disease transmission.
自噬在许多生物体抵抗病原体感染方面发挥着重要作用；然而，对于媒介传播的动植物病原体，相关研究较少，这些病原体有时会在其媒介中复制并造成有害影响。番茄韧皮部杆菌（CLso）是一种苛求的革兰氏阴性、局限于韧皮部的植物病原体，由胡萝卜木虱传播。这种细菌引起的植物病害称为胡萝卜黄化病，由于全球范围内的巨大经济损失，最近受到了广泛关注。在此，我们证明钙ATP酶、胞质钙，以及最重要的Beclin-1在调节自噬及其与木虱体内番茄韧皮部杆菌的关联中发挥作用。番茄韧皮部杆菌的存在会产生活性氧，并诱导木虱中肠（细菌传播的主要部位）中解毒酶的表达。番茄韧皮部杆菌还会诱导中肠中肌浆网/内质网Ca2+泵（SERCA）和1,4,5-三磷酸肌醇受体（ITPR）的表达，导致细胞胞质中钙水平升高。单独沉默这些基因会破坏胞质中的钙水平，并直接影响自噬，进而影响番茄韧皮部杆菌的存活和传播。通过不同的钙诱导激酶抑制Beclin1磷酸化会改变自噬的表达以及番茄韧皮部杆菌的滴度和存活情况。基于我们从中肠获得的结果，我们认为胞质钙水平、自噬与番茄韧皮部杆菌在胡萝卜木虱体内的存活和传播之间存在直接关联。重要性由媒介传播的韧皮部杆菌属物种引起的植物病害是许多农业部门最重要的经济损失原因。预防这些病害主要依赖于对昆虫媒介进行化学喷雾。基于知识对细菌与媒介相互作用的干预作为一种可持续解决方案仍然是一种有前景的方法。为了弄清楚韧皮部杆菌如何利用其昆虫媒介中的分子途径进行传播，在此我们表明该细菌会操纵内质网膜两侧的钙水平，从而操纵自噬。沉默与这些途径相关的基因会破坏胞质中的钙水平，并直接影响自噬和韧皮部杆菌的传播。这些结果证明了可用于操纵和控制疾病传播的主要途径。
