A characteristic feature of grasses and commercially important cereals is the presence of (1,3;1,4)-β- d -glucans in their cell walls. We have used comparative genomics to link a major quantitative trait locus for (1,3;1,4)-β- d -glucan content in barley grain to a cluster of cellulose synthase–like CslF genes in rice. After insertion of rice CslF genes into Arabidopsis , we detected (1,3;1,4)-β- d -glucan in walls of transgenic plants using specific monoclonal antibodies and enzymatic analysis. Because wild-type Arabidopsis does not contain CslF genes or have (1,3;1,4)-β- d -glucans in its walls, these experiments provide direct, gain-of-function evidence for the participation of rice CslF genes in (1,3;1,4)-β- d -glucan biosynthesis.

Transcription factors (TFs) play a significant role in signal transduction networks spanning the perception of a stress signal and the expression of corresponding stress-responsive genes. TFs are multi-functional proteins that may simultaneously control numerous pathways during stresses in plants—this makes them powerful tools for the manipulation of regulatory and stress-responsive pathways. In recent years, the structure-function relationships of numerous plant TFs involved in drought and associated stresses have been defined, which prompted devising practical strategies for engineering plants with enhanced stress tolerance. Vast data have emerged on purposely basic leucine zipper (bZIP), WRKY, homeodomain-leucine zipper (HD-Zip), myeloblastoma (MYB), drought-response elements binding proteins/C-repeat binding factor (DREB/CBF), shine (SHN), and wax production-like (WXPL) TFs that reflect the understanding of their 3D structure and how the structure relates to function. Consequently, this information is useful in the tailored design of variant TFs that enhances our understanding of their functional states, such as oligomerization, post-translational modification patterns, protein-protein interactions, and their abilities to recognize downstream target DNA sequences. Here, we report on the progress of TFs based on their interaction pathway participation in stress-responsive networks, and pinpoint strategies and applications for crops and the impact of these strategies for improving plant stress tolerance.

It has been suggested that tannin extraction from grape berries into wine is limited by tannin binding to cell walls. Here we review the current state of knowledge and identify gaps in research that would enable characterisation of these interactions. Such characterisation could improve tannin extraction management in winemaking. The work identified in this review supports the hypothesis that tannin–cell wall interactions are formed by hydrogen bonding and hydrophobic interactions with the binding capacity of the cell walls influenced by tannin and polysaccharide structure and composition. Cell wall changes during berry development may increase the tannin-binding capacity of cell walls, while tannin structure may also influence its affinity for cell wall material. This review also identifies the need to investigate cultural and environmental factors that affect tannin and polysaccharide composition, to characterise the tannin-binding capacity of cell walls and to develop methods for assessing tannin-binding capacity of fruit prior to harvest. It is envisaged that a detailed understanding of tannin interactions with other components in the grape would lead to a predictive model for extractability of condensed tannins into wine.R.L. Hanlin, M. Hrmova, J.F. Harbertson and M.O. Downe

The HKT family of Na⁺ and Na⁺/K⁺ transporters is implicated in plant salinity tolerance. Amongst these transporters, the cereal HKT1;4 and HKT1;5 are responsible for Na⁺ exclusion from photosynthetic tissues, a key mechanism for plant salinity tolerance. It has been suggested that Na⁺ is retrieved from the xylem transpiration stream either in the root or the leaf sheath, protecting the leaf blades from excessive Na⁺ accumulation. However, direct evidence for this scenario is scarce. Comparative modeling and evaluation of rice (Oryza sativa) HKT-transporters based on the recent crystal structure of the bacterial TrkH K⁺ transporter allowed to reconcile transcriptomic and physiological data. For OsHKT1;5, both transcript abundance and protein structural features within the selectivity filter could control shoot Na⁺ accumulation in a range of rice varieties. For OsHKT1;4, alternative splicing of transcript and the anatomical complexity of the sheath needed to be taken into account. Thus, Na⁺ accumulation in a specific leaf blade seems to be regulated by abundance of a correctly spliced OsHKT1;4 transcript in a corresponding sheath. Overall, allelic variation of leaf blade Na⁺ accumulation can be explained by a complex interplay of gene transcription, alternative splicing and protein structure.