Figure 9.

Central role of ZCCT2 in the redox control of freezing tolerance and the initial development of flower primordia. The redox compounds and osmotica induced different timing and level of changes in the E_GSH/GSSG value and subsequently in ZCCT2 expression in Cheyenne (Ch, left side) and T. spelta (Tsp, right side). The chemical treatments induced a great increase in E_GSH/GSSG value after 3 d at 20/17°C in Ch and during the subsequent cultivation for 4 d at 5°C in Tsp. Higher ZCCT2 transcript levels in Ch were generally associated with greater expression of genes (CBF14, APSR, sAPX1) that contribute to increased freezing tolerance. NF-YB may affect ZCCT2 in a regulatory loop, which also influences the ABA-dependent freezing tolerance through NCED1. The lower level of ZCCT2 in Tsp was associated with induction of the regulators activating the initial development of flower primordia (OXS2, FKF1, VRN1). Based on the correlation analysis, ABA (NCED1) may also be involved in the redox-dependent regulation of the initial development of flower primordia. Continuous lines indicate the proposed relationship between two parameters based on the correlation analysis (thin line: moderate correlation, thick line: close correlation) and broken lines refer to data from the literature indicated by the corresponding numbers.