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Only a handful of model systems for studying programmed cell death (PCD) exist. The model Arabidopsis thaliana has generated a plethora of knowledge, but it is essential to introduce new models to broaden our understanding of the commonalities of PCD. This review focuses on Aponogeton madagascariensis (the lace plant) as a choice model to study PCD in vivo. PCD plays a key role in plant development and defence. Thus, identifying key regulators across plants is a priority in the field. The formation of perforations in lace plant leaves in areas called areoles is a striking example of PCD. Cells undergoing PCD within areoles can be easily identified from a loss of their anthocyanin pigmentation. In contrast, cells adjacent to veins, non-PCD cells, retain anthocyanins, creating a gradient of cell death. The spatiotemporal pattern of perforation formation, a gradient of cell death within areoles, and the availability of axenic cultures provide an excellent in vivo system to study mechanisms of developmental PCD. The priorities to further develop this model involve sequencing the genome, establishing transformation protocols, and identifying anthocyanin species to determine their medicinal properties. We discuss practical methodologies and challenges associated with developing the lace plant as a model to study PCD. Key words: lace plant, novel model organism, anthocyanin, leaf development, perforation formation, gradient of cell death Programmed cell death models, Programmed cell death (PCD) is a ubiquitous cellular process for the controlled demise of the cell either to achieve a developmental step or in response to stress (Kuriyama and Fukuda [...]

Upon gamete fusion, animal egg cells secrete proteases from cortical granules to establish a fertilization envelope as a block to polyspermy.sup.1-4. Fertilization in flowering plants is more complex and involves the delivery of two non-motile sperm cells by pollen tubes.sup.5,6. Simultaneous penetration of ovules by multiple pollen tubes (polytubey) is usually avoided, thus indirectly preventing polyspermy.sup.7,8. How plant egg cells regulate the rejection of extra tubes after successful fertilization is not known. Here we report that the aspartic endopeptidases ECS1 and ECS2 are secreted to the extracellular space from a cortical network located at the apical domain of the Arabidopsis egg cell. This reaction is triggered only after successful fertilization. ECS1 and ECS2 are exclusively expressed in the egg cell and transcripts are degraded immediately after gamete fusion. ECS1 and ESC2 specifically cleave the pollen tube attractor LURE1. As a consequence, polytubey is frequent in ecs1 ecs2 double mutants. Ectopic secretion of these endopeptidases from synergid cells led to a decrease in the levels of LURE1 and reduced the rate of pollen tube attraction. Together, these findings demonstrate that plant egg cells sense successful fertilization and elucidate a mechanism as to how a relatively fast post-fertilization block to polytubey is established by fertilization-induced degradation of attraction factors. Fertilized Arabidopsis egg cells secrete endopeptidases into the extracellular space that cleave the pollen tube attractor LURE1, preventing polytubey., Author(s): Xiaobo Yu [sup.1] , Xuecheng Zhang [sup.1] , Peng Zhao [sup.1] , Xiongbo Peng [sup.1] , Hong Chen [sup.1] , Andrea Bleckmann [sup.2] , Anastasiia Bazhenova [sup.2] , Ce [...]

An important component of cellular biochemistry is the concentration of proteins and nucleic acids in non-membranous compartments.sup.1,2. These biomolecular condensates are formed from processes that include liquid-liquid phase separation. The multivalent interactions necessary for liquid-liquid phase separation have been extensively studied in vitro.sup.1,3. However, the regulation of this process in vivo is poorly understood. Here we identify an in vivo regulator of liquid-liquid phase separation through a genetic screen targeting factors required for Arabidopsis RNA-binding protein FCA function. FCA contains prion-like domains that phase-separate in vitro, and exhibits behaviour in vivo that is consistent with phase separation. The mutant screen identified a functional requirement for FLL2, a coiled-coil protein, in the formation of FCA nuclear bodies. FCA reduces transcriptional read-through by promoting proximal polyadenylation at many sites in the Arabidopsis genome.sup.3,4. FLL2 was required to promote this proximal polyadenylation, but not the binding of FCA to target RNA. Ectopic expression of FLL2 increased the size and number of FCA nuclear bodies. Crosslinking with formaldehyde captured in vivo interactions between FLL2, FCA and the polymerase and nuclease modules of the RNA 3'-end processing machinery. These 3' RNA-processing components colocalized with FCA in the nuclear bodies in vivo, which indicates that FCA nuclear bodies compartmentalize 3'-end processing factors to enhance polyadenylation at specific sites. Our findings show that coiled-coil proteins can promote liquid-liquid phase separation, which expands our understanding of the principles that govern the in vivo dynamics of liquid-like bodies. A genetic screen for factors required by the Arabidopsis RNA-binding protein FCA identifies FLL2 as necessary in the formation of FCA nuclear bodies, and thus a role for FLL2 in liquid-liquid phase separation., Author(s): Xiaofeng Fang [sup.1] , Liang Wang [sup.2] , Ryo Ishikawa [sup.1] [sup.5] , Yaoxi Li [sup.1] , Marc Fiedler [sup.3] , Fuquan Liu [sup.1] [sup.6] , Grant Calder [sup.1] [...]

Byline: Y. Fan, H. Li, R. Fan, H. Zhang, X. Zhao and B. Li Key words: ZmFLS1; Flavonols; Oxidative stress; MDA (Malondialdehyde) INTRODUCTION Biological and abiotic stresses promote the accumulation [...]

Plant vacuoles are multifunctional organelles with dynamic and transient membranous structures, such as trans-vacuolar strands and bulbs. Bulbs are highly mobile structures that travel along trans-vacuolar strands. A candidate effector [...]

Thioredoxins (TRXs) are important components of redox-regulated systems involved in maintaining and regulating the cellular redox environment during growth and development and in response to abiotic and biotic stresses. Plants possess several types of TRX localized in various compartments, including five different types of chloroplastic TRXs. Arabidopsis thaliana contains two chloroplastic type-f TRXs, TRX f1 and TRX f2, involved in the regulation of light-dependent activation of photosynthesis and carbon metabolism. However, little is known about their role during development and in response to stress. We used single and double mutants of TRX f1 and TRX f2 to assess their roles during seed germination and seedling development. Loss of both TRX f1 and TRX f2 induced faster germination and seedling development associated with reduced sensitivity to abscisic acid. This suggests that type-f TRXs negatively regulate seed germination and seedling development. Moreover, doublemutant seedlings were more sensitive to methyl viologen and UV-C irradiation than the wild-type seedlings, indicating that loss of type-f TRXs increases sensitivity to oxidative stress. Overall, these results indicate that type-f TRXs contribute to maintaining an adequate cellular environment required for a tight regulation of germination and a better tolerance to oxidative stress. Keywords:Arabidopsis thaliana, germination, oxidative stress, type-f thioredoxin, UV-C. Les thiorédoxines (TRX) sont des enzymes d'oxydoréduction qui régulent l'état redox cellulaire pendant le développement et en réponse au stress. Les plantes possèdent plusieurs types de TRX dans différents organites cellulaires, incluant cinq TRX chloroplastiques. Arabidopsis thaliana possède deux TRX chloroplastiques de type f impliquées dans la photosynthèse et le métabolisme carboné. Cependant, les rôles des TRX f pendant le développement et en réponse au stress sont peu connus. Pour préciser ces rôles, de simples et double mutants de TRX f1 et TRX f2 ont été analysés pendant la germination et le développement des plantules. La perte des deux isoformes a accéléré la germination et le développement des plantules tout en diminuant la sensibilité à l'ABA, suggérant que les TRX frégulent négativement la germination et le développement des plantules. De plus, les plantules des doubles mutants étaient davantage sensibles au méthyle viologène et aux rayons UV-C que les plantules sauvages, démontrant que l'absence des TRX f augmente la sensibilité au stress oxydatif. Ces résultats suggèrent que les TRX de type f contribuent à maintenir un environnement cellulaire qui favorise un contrôle rigoureux de la germination et une plus grande tolérance au stress oxydatif. Mots-clés : Arabidopsis thaliana, germination, stress oxydatif, thiorédoxine de type-f, UV-C., Introduction Plant cells continuously produce reactive oxygen species (ROS) such as superoxides and peroxides during the processes of photosynthesis and respiration. While precise levels of ROS are important for regulating [...]

Author(s): Elwira Smakowska-Luzan [1]; G. Adam Mott [2]; Katarzyna Parys [1]; Martin Stegmann [3]; Timothy C Howton [4]; Mehdi Layeghifard [2]; Jana Neuhold [5]; Anita Lehner [5]; Jixiang Kong [1]; [...]

Byline: Z. Shah, G S. Ali, A. El-Sayed, M. Hussain, H. Shah, M. Z. Ahmad, N. Ahmad and A. Iqbal Key words: HsfA1d, subcellular localization, yellow florescent proteins, gateway cloning, [...]