Evaluation of antifungal plant extracts against cereal and legume seed-borne pathogens for effective management

Sri Lanka as an agricultural country needs to manage the seed-borne fungal pathogens that have caused infections and diseases that result in significant crop losses and a decline in yield and productivity.Therefore,it is imperative to apply pathogen management strategies that are environmentally friendly,and economically feasible such as plant extractions,to reduce seed-borne fungi and increase the quality of the seed.This study was aimed at identifying the antifungal efficacy of Allium sativum,Aloe vera,Azadirachta indica,and Zingiber officinale extracts and their effective concentrations to control the seed-borne fungal pathogens;Aspergillus flavus,A.niger,Orbilia foliicola,Rhizopus oryzae,and Talaromyces oumae-annae isolated from Arachis hypogea,Oryza sativa,Vigna radiata,and V.sinensis respectively.Antifungal efficacy was determined by the agar well diffusion method and poisoned food technique.Plant extracts’effectiveness for seed germination and seed quality was evaluated by pot experiments.Zingiber officinale crude extract exhibited the highest antifungal activity against the tested pathogens which was as effective as Captan 50%(WP),a positive control.Further analysis of the results from the pot experiment revealed that O.sativa,and V.radiata seeds treated with A.indica,and Z.officinale aqueous extracts showed 100%germination percentage.Azadirachta indica,and Z.officinale aqueous extracts are the most effective in promoting seed germination and seedling vigor while A.vera extract is the least effective extract.Comparing the two different extracts,aqueous extracts significantly promote seed germination and increase seedling vigor.

New records of Hypoxylon hypomiltum and Hypomontagnella monticulosa from Pilikuththuwa lowland wet zone forest,Sri Lanka

Species of Hypoxylon exhibit their highest diversity in the tropics.During an assessment of diversity of hypoxylaceous fungi in the lowland wet zone forest area in Sri Lanka,two new records were reported.Morphological identification of the collected samples was carried out using both macroscopic and microscopic characteristics.Genomic DNA was extracted using modified CTAB method and amplification of both ITS andβ-tubulin genes were performed using ITS1 and ITS4 and T1 and T22 primers respectively.In the present study,recognition of species in Hypoxylon was carried out using a combined phylogenic analysis of ITS andβ-tubulin molecular markers.Phylogenetic tree resulted from combined analysis comprised nine clades.According to the results,two new country records of Hypomontagnella monticulosa and Hypoxylon hypomiltum were recognized from Pilikuththuwa lowland wet zone forest.

Control of Directional Macromolecular Trafficking Across Specific Cellular Boundaries:A Key to Integrative Plant Biology

There is now solid evidence that cell-to-cell trafficking of certain proteins and RNAs plays a critical role in trans-cellular regulation of gene expression to coordinate cellular differentiation and development. Such trafficking also is critical for viral infection and plant defense. The mechanisms of trafficking remain poorly understood. Although some proteins may move between cells by diffusion, many proteins and RNAs move in a highly regulated fashion. Regulation is likely achieved through interactions between distinct protein or RNA motifs and cellular factors. Some motifs and factors have been identified. One of the major focuses for future studies is to identify all motifs and their cognate factors and further elucidate their roles in trafficking between specific cells. With increasing information from such studies, we should be able to develop an understanding of the mechanisms that regulate trafficking of various proteins and RNAs across all and specific cellular boundaries. On the basis of such mechanistic knowledge, we can further investigate how the trafficking machinery has evolved to regulate developmental and physiological processes in a plant, how pathogens have co-evolved to use this machinery for systemic spread in a plant, and how plants use this machinery for counterdefense.

The Formation of Anthocyanic Vacuolar Inclusions in Arabidopsis thaliana and Implications for the Sequestration of Anthocyanin Pigments

Anthocyanins are flavonoid pigments that accumulate in the large central vacuole of most plants. Inside the vacuole, anthocyanins can be found uniformly distributed or as part of sub-vacuolar pigment bodies, the Anthocyanic Vacuolar Inclusions （AVIs）. Using Arabidopsis seedlings grown under anthocyanin-inductive conditions as a model to un- derstand how AVIs are formed, we show here that the accumulation of AVIs strongly correlates with the formation of cyanidin 3-glucoside （C3G） and derivatives. Arabidopsis mutants that fail to glycosylate anthocyanidins at the 5-0 position （Sgt mutant） accumulate AVIs in almost every epidermal cell of the cotyledons, as compared to wild-type seedlings, where only a small fraction of the cells show AVIs. A similar phenomenon is observed when seedlings are treated with vanadate. Highlighting a role for autophagy in the formation of the AVIs, we show that various mutants that interfere with the autophagic process （atg mutants） display lower numbers of AVIs, in addition to a reduced accumulation of anthocyanins. Interestingly, vanadate increases the numbers of AVIs in the atg mutants, suggesting that several pathways might participate in AVl formation. Taken together, our results suggest novel mechanisms for the formation of sub-vacuolar compartments capable of accumulating anthocyanin pigments.

Gene expression and physiological responses to salinity and water stress of contrasting durum wheat genotypes

Elucidating the relationships between gene expression and the physiological mechanisms remains a bottleneck in breeding for resistance to salinity and drought. This study related the expression of key target genes with the physiological performance of durum wheat under different combinations of salinity and irrigation. The candidate genes assayed included two encoding for the DREB（dehydration responsive element binding） transcription factors Ta DREB1 A and Ta DREB2 B, another two for the cytosolic and plastidic glutamine synthetase（Ta GS1 and Ta GS2）, and one for the specific Na^＋/H^＋ vacuolar antiporter（Ta NHX1）. Expression of these genes was related to growth and different trait indicators of nitrogen metabolism（nitrogen content, stable nitrogen isotope composition, and glutamine synthetase and nitrate reductase activities）, photosynthetic carbon metabolism（stable carbon isotope composition and different gas exchange traits） and ion accumulation. Significant interaction between genotype and growing conditions occurred for growth, nitrogen content, and the expression of most genes.In general terms, higher expression of Ta GS1, Ta GS2,Ta DREB2 B, and to a lesser extent of Ta NHX1 were associated with a better genotypic performance in growth, nitrogen, and carbon photosynthetic metabolism under salinity and water stress. However, Ta DREB1 A was increased in expression under stress compared with control conditions, with tolerant genotypes exhibiting lower expression than susceptible ones.

Viroids:Small Probes for Exploring the Vast Universe of RNA Trafficking in Plants

Cell-to-cell and long-distance trafficking of RNA is a rapidly evolving frontier of integrative plant biology that broadly impacts studies on plant growth and development, spread of infectious agents and plant defense responses. The fundamental questions being pursued at the forefronts revolve around function, mechanism and evolution. In the present review, we will first use specific examples to illustrate the biological importance of cell-to-cell and long-distance trafficking of RNA. We then focus our discussion on research findings obtained using viroids that have advanced our understanding of the underlying mechanisms involved in RNA trafficking. We further use viroid examples to illustrate the great diversity of trafficking machinery evolved by plants, as well as the promise for new insights in the years ahead. Finally, we discuss the prospect of integrating findings from different experimental systems to achieve a systems-based understanding of RNA trafficking function, mechanism and evolution.

CONSTANS alters the circadian clock in Arabidopsis thaliana

Plants are sessile organisms that have acquired highly plastic developmental strategies to adapt to the environment.Among these processes,the floral transition is essential to ensure reproductive success and is finelyregulated by several internal andexternal genetic networks.The photoperiodic pathway,which controls plant response to day length,is one of the most important pathways controlling flowering.In Arabidopsis photoperiodic flowering,CONSTANS(CO)is the central gene activating the expression of the florigen FLOWERING LOCUS T(FT)in the leaves at the end of a long day.The circadian clock strongly regulates Co expression.However,to date,no evidence has been reported regarding a feedbackloop from the photoperiod pathway back to the circadian clock.Using transcriptional networks,we have identified relevant network motifs regulating the interplay between the circadian clock and the photoperiod pathway.Gene expression,chromatin immunoprecipitation experiments,and phenotypic analysis allowed us to elucidate the role of Co over the circadian clock.Plants with altered cO expression showed a different internal clock period,measured by daily leaf rhythmic movements.We showed that co upregulates the expression of key genes related to the circadian clock,such as CCA1,LHY,PRR5,and Gl,at the end of a long day by bindingto specific sites on their promoters.Moreover,a high numberof PRR5-repressed target genes are upregulated by CO,and this could explain the phase transition promoted by CO.The CO-PRR5 complex interacts with the bZiP transcriptionfactor HY5andhelps to localize the complex in the promoters of clock genes.Taken together,our results indicate that there may be a feedback loop in which co communicates back to the circadian clock,providing seasonal information to the circadian system.

The Arabidopsis bZIP1 Transcription Factor Is Involved in Sugar Signaling, Protein Networking, and DNA Binding

Sugar signaling is a mechanism that plants use to integrate various internal and external cues to achieve nutrient homeostasis, mediate developmental programs, and articulate stress responses. Many bZlP transcription factors are known to be involved in nutrient and/or stress signaling. An Arabidopsis Sl-group bZlP gene, AtbZIP1, was identified as a sugar-sensitive gene in a previous gene expression profiling study （Plant Cell. 16, 2128-2150）. In this report, we show that the expression of AtbZIP1 is repressed by sugars in a fast, sensitive, and reversible way. The sugar repression of Atb- ZIP1 is affected by a conserved sugar signaling component, hexokinase. Besides being a sugar-regulated gene, AtbZIP1 can mediate sugar signaling and affect gene expression, plant growth, and development. When carbon nutrients are limited, gain or loss of function of AtbZlP1 causes changes in the rates of early seedling establishment. Results of phenotypic analyses indicate that AtbZlP1 acts as a negative regulator of early seedling growth. Using gain- and loss-of-function plants in a microarray analysis, two sets of putative AtbZIP1-regulated genes have been identified. Among them, sugar-responsive genes are highly over-represented, implicating a role of AtbZlP1 in sugar-mediated gene expression. Using yeast two-hybrid （Y-2-H） screens and bimolecular fluorescence complementation （BiFC） analyses, we are able to recapitulate extensive C/S1 AtbZlP protein interacting network in living cells. Finally, we show that AtbZIP1 can bind ACGT-based motifs in vitro and that the binding characteristics appear to be affected by the heterodimerization between AtbZlP1 and the C-group AtbZIPs, including AtbZlP10 and AtbZlP63.

Special issue:The contributions of Erio Camporesi

We are proud to publish a special issue of Fungal Diversity in honour of the contributions made by Erio Camporesi,who has promoted mycological research as a prodigious amateur mycologist and collector of fungi.The special issue includes Fungal Diversity notes 11,with many taxa named in Erio’s honour and a monograph of hyaline-spored Coelomycetes,both incorporating many of Erio’s collections.