Bernard Dell

Wheat Avenin-like proteins (TaALP) are atypical storage proteins belonging to the Prolamin superfamily. Previous studies on ALPs have focused on the proteins’ positive effects on dough strength, whilst no correlation has been made between TaALPs and the plant immune system. Here, we performed genome-wide characterization of ALP encoding genes in bread wheat. In silico analyses indicated the presence of critical peptides in TaALPs that are active in the plant immune system. Pathogenesis-related nucleotide motifs were also identified in the putative promoter regions of TaALP encoding genes. RT-PCR was performed on TaALP and previously characterised pathogenesis resistance genes in developing wheat caryopses under control and Fusarium graminearum infection conditions. The results showed that TaALP and NMT genes were upregulated upon F. graminearum inoculation. mRNA insitu hybridization showed that TaALP genes were expressed in the embryo, aleurone and sub-aleurone layer cells. Seven TaALP genes were cloned for the expression of recombinant proteins in Escherichia coli, which displayed significant inhibitory function on F. graminearum under anti-fungal tests. In addition, FHB index association analyses showed that allelic variations of two ALP genes on chromosome 7A were significantly correlated with FHB symptoms. Over-expression of an ALP gene on chromosome 7A showed an enhanced resistance to FHB. Yeast two Hybridization results revealed that ALPs have potential proteases inhibiting effect on metacaspases and beta-glucosidases. A vital infection process related pathogen protein, F. graminearum Beta-glucosidase was found to interact with ALPs. Our study is the first to report a class of wheat storage protein or gluten protein with biochemical functions. Due to its abundance in the grain and the important multi-functions, the results obtained in the current study are expected to have a significant impact on wheat research and industry.

This paper reports on a new disorder that first appeared in eucalypt plantations in south China in 2003. The plantations were destructively sampled near Zeizhou, Yanxi, Kaiping and Gaoyao in September to December 2003. Whilst some 5% of 0.5 to 1.5 year-old Eucalyptus urophylla trees declined rapidly and exhibited symptoms of wilting, the majority of the affected trees declined slowly and exhibited two foliar symptoms. Young leaves initially developed an interveinal chlorosis extending from the leaf margin inwards to the midrib. Most leaves then developed pockets of necrotic tissue that became bleached but typically had brown margins. The former symptoms have been recognised as being caused by limited boron supply in soil but the latter symptoms have not been previously observed in eucalypts in China. Inorganic analysis showed that the leases with the latter symptoms had deficient B concentrations whereas the leaves from healthy trees had adequate B concentrations. Bacterial wilt, Ralstonia solanacearum, was present at all sites where foliar symptoms and tree death were present. The root system of all trees with foliar chlorosis and necrosis had signs of infection in some roots and attrition of lateral roots. The trunk and branches of the recently died trees and the trees with advanced leaf drop had discoloured xylem, which on cutting, oozed bacterial slime. Possible relationships between root damage caused by abiotic (e.g. typhoons, root damage from hand weeding) and biotic factors and reduced B uptake are discussed. Recommendations are made for reducing bacterial wilt disease and improving B management in fast-growing short-rotation eucalypt plantations.

The tuart forest and woodlands contain a rich diversity of higher fungi. Because of the known benefit of symbiotic fungi that form associations with roots (known as mycorrhizas), this component of the Tuart Project is focussing on fungi in this group. Examination of the roots of tuart seedlings grown in pots of soil collected from under healthy tuart in the field showed that the most abundant type of mycorrhizas are those formed with higher fungi such as the toadstools, puffballs and truffle-like fungi.

Over the last 10 years, tuart trees in the Yalgorup region of south-western Australia have been undergoing an alarming period of decline and dieback. Research into the cause of the decline indicates the possible involvement of a complex disease syndrome involving a number of unknown factors contributing to the overall reduction in health. Factors affecting nutrient supply and availability have been suggested as playing a role in the decline. Tuart belongs to the largest Eucalyptus subgenus Symphyomyrtus but is taxonomically distinct, having no close relatives and thus forming a monospecific section (Ruthrof et al. 2002). The Symphyomyrtus species has a greater demand for calcium, magnesium, and probably potassium whereas Monocalyptus has a greater demand for magnesium. Such differences must have a physiological basis but as yet no explanation has been offered (Judd et al. 1996). The nutrient status of tuart has been largely unknown, creating a gap in our knowledge in the role of nutrient supply to healthy tuart trees. Therefore, there has been an obvious need to investigate the current nutrient status of both healthy and declining tuart in native plant communities along the Swan Coastal Plain and further determine the role of particular macro and/or micronutrients in the decline.