Expression of antiapoptotic genes bcl-xL and ced-9 in tomato enhances tolerance to viral-induced necrosis and abiotic stress

Abstract

D satellite RNA (satRNA) is a strain of cucumber mosaic virus (CMV) satRNA that induces an epidemic lethal disease in tomato. No natural resistance or tolerance has ever been found. Previously, we demonstrated the involvement of programmed cell death in disease development. Here, transgenic tomato plants expressing animal antiapoptotic genes bcl-xL and ced-9 were generated through agrobacterium-mediated transformation. High expression of bcl-xL or ced-9 affected plant growth and seed development. Inoculation of seedlings with CMV͞D satRNA at T 1 and T2 generations resulted in delayed cell-death symptoms or absence of symptoms. The degree of symptom suppression was correlated with increasing expression levels of the transgenes. Survival rates were compared among inoculated transgenic lines expressing bcl-xL, ced-9, and bcl-xL (G138A), a loss-of-function mutant of bcl-xL. More than 80% of the bcl-xL and ced-9 T 1 transgenic lines showed higher survival rates than the average for bcl-xL (G138A) transgenic lines. Total RNA extracted from surviving plants contained D satRNA, indicating systemic accumulation of D satRNA. Thus, expression of bcl-xL and ced-9 improved tolerance to, rather than resistance to, CMV͞D satRNA infection. In addition, expression of bcl-xL and ced-9 specifically abrogated the formation of necrotic lesions, but not other symptoms, in tomato leaves during chilling at 4°C. At 7°C, temperature-induced leaf senescence was dramatically delayed in bcl-xL and ced-9 transgenic plants, and high levels of anthocyanins accumulated, possibly limiting oxidative stress. Hence, expression of these animal antiapoptotic genes improved plant survival under abiotic or biotic stress.

The ArabidopsisBAP1andBAP2Genes Are General Inhibitors of Programmed Cell Death

“…Plants may use an apoptotic machinery similar to those of animals and yeast (Saccharomyces cerevisiae) as similar morphological and biochemical features are shared for PCD in these organisms (Gilchrist, 1998;Beers and McDowell, 2001; Greenberg and Yao, 2004;Lam, 2004). Furthermore, cell death in plants is suppressed by expression of an animal antiapoptosis gene CED9/Bcl-2 (Mitsuhara et al, 1999;Dickman et al, 2001), and an HR-like cell death is induced by the expression of animal proapoptotic genes such as Bax (Lacomme and Santa Cruz, 1999;Mitsuhara et al, 1999;Xu et al, 2004). However, functional equivalents of animal cell death genes have not been readily identified by sequence homology in plants and the regulation and execution of PCD in plants have yet to be understood.…”

Fungal pathogen protection in transgenic lettuce by expression of a apoptosis related Bcl-2 gene

“…기존의 단일유전자의 도입을 통한 내병 성 및 내재해성 작물의 육성은 결과적으로 한계점에 봉 착하고 있으며 내병성의 경우 바이러스병에 대해 coat protein 유전자를 도입한 경우에만 저항성을 나타내었으 나 이 경우에도 세대가 진전될수록 저항성의 정도가 불 안정하게 나타났고, 특히 곰팡이병의 경우에는 단일유전 자의 도입으로 내병성작물을 육종하는 것은 지금까지의 경험으로 비추어 볼 때 어려운 것으로 사료 된다. 본 실 험에서 사용된 Bcl-2 family에 속하는 유전자는 apoptosis 의 조절에 관여하고 있는 것으로 알려져 있다 (Dickman et al 2001;Li et al 2004;Xu et al 2004). 나아가 이 유전자 들은 식물의 발달과정에 중요한 역할을 하며 특히 세균, 곰팡이 및 바이러스와 같은 병원균과 식물체간의 상호 기작에 크게 관여하는 것으로 보고되고 있다 (Dangl and Jones 2001;Yin et al 2004;Xu et al 2004 Agrobacterium.…”

Inhibitor of Apoptosis (IAP)-like Protein Lacks a Baculovirus IAP Repeat (BIR) Domain and Attenuates Cell Death in Plant and Animal Systems

“…For example, homologues of the mammalian Bax-inducible cell death inhibitor BI-1 have been identified in several plants, including Arabidopsis, rice, tobacco, and barley (47)(48)(49)(50). In addition, animal apoptotic regulators, such as human Bcl-2 and Bcl-xl as well as nematode CED-9, can either induce or suppress cell death in transgenic plants (51)(52)(53). In plants, PCD occurs during developmental processes, such as flower development, embryogenesis, seed germination, and vessel and trachea formation.…”