Tissue-specific changes in apoplastic proteins and cell wall structure during cold acclimation of winter wheat crowns

Abstract

Changes in the apoplast associated with cell wall modifications and anti-freeze proteins in the shoot apical meristem and vascular transition zone suggest differential acclimation responses within the winter wheat crown.

Ice segregation in the crown of winter cereals: Evidence for extraorgan and extratissue freezing

“…Cold‐acclimated oat crowns recovering from freezing injury were reported to have a suberized band of cells between the VTZ and SAM (Livingston & Tuong, ). This band of cells denoted as the intermediate zone (Gusta et al, ) was observed with a tetrazolium chloride viability stain as the boundary of crown injury in recovering Norstar winter wheat (Willick et al, ) and Wintok winter oat (Livingston et al, ). It is possible the crown survives freezing because this intermediate region acts as a barrier to ice propagation, thus allowing the SAM to avoid ice propagation from the leaf sheath or VTZ.…”

“…Due to the complex nature of the crown, not all its constituents achieve the same level of hardiness (Chen, Gusta, & Fowler, ; Livingston et al, ; Olien, ; Tanino & McKersie, ; Willick, Takahashi, Fowler, Uemura, & Tanino, ). Initial crown injury in cold‐acclimated winter wheat ( Triticum aestivum L.) was observed at −10°C in the VTZ (Willick et al, ). The SAM is injured at or near the plant LT 50 , or the temperature at which half the plants recovered from freezing.…”

“…Extratissue freezing is commonly associated with the formation of large ice crystals in xylem tissue. In frozen cold‐acclimated winter cereal crowns, the VTZ has a proportionally high volume of water relative to the remainder of the crown (Gusta, Fowler, Chen, Russell, & Stout, ; Olien, ) and is injured before the SAM (Chen et al, ; Tanino & McKersie, ; Willick et al, ). The xylem associated with the VTZ may undergo extratissue freezing and act as an ice sink relative to the SAM, similar to extratissue freezing observed in the lacuna of Buxus smpervirens Pojark.…”

“…Because the VTZ is the site of critical root meristem cells, it is unable to act as an ice sink. Winter wheat does have a visually analogous bud scale structure, known as the leaf sheath, encapsulating the SAM and upper one third of the VTZ (Willick et al, ). If extraorgan freezing occurs in cold‐acclimated winter cereal crowns, then supercooling of the SAM and desiccation of the VTZ corresponded with a loss of water and a low INA relative to the leaf sheath.…”

Cytoplasmic and nuclear genetic components of membrane stability of winter wheat plants exposed to sub‐zero temperatures

“…These responses may differ on a tissue‐specific basis. For example, Willick, Takahashi, Fowler, Uemura, and Tanino () found that the protein profiles of apoplastic fluid extracted from shoot apical meristem tissue differed remarkably from that from vascular transition zone tissue in cold‐acclimated winter wheat plants, even though the tissues were physically separated by less than 1 cm. Identification of differences in the ability to effect these kinds of responses and the genetic control of those differences may provide a new avenue of approach to developing wheat lines with enhanced ability to tolerate freezing stress.…”