The influence of vernalization and daylength on expression of flowering-time genes in the shoot apex and leaves of barley (Hordeum vulgare).

Responses to prolonged low-temperature treatment of imbibed seeds (vernalization) were examined in barley (Hordeum vulgare). These occurred in two phases: the perception of prolonged cold, which occurred gradually at low temperatures, and the acceleration of reproductive development, which occurred after vernalization. Expression of the VERNALIZATION1 gene (HvVRN1) increased gradually in germinating seedlings during vernalization, both at the shoot apex and in the developing leaves. This occurred in darkness, independently of VERNALIZATION2 (HvVRN2), consistent with the hypothesis that expression of HvVRN1 is induced by prolonged cold independently of daylength flowering-response pathways. After vernalization, expression of HvVRN1 was maintained in the shoot apex and leaves. This was associated with accelerated inflorescence initiation and with down-regulation of HvVRN2 in the leaves. The largest determinant of HvVRN1 expression levels in vernalized plants was the length of seed vernalization treatment. Daylength did not influence HvVRN1 expression levels in shoot apices and typically did not affect expression in leaves. In the leaves of plants that had experienced a saturating seed vernalization treatment, expression of HvVRN1 was higher in long days, however. HvFT1 was expressed in the leaves of these plants in long days, which might account for the elevated HvVRN1 expression. Long-day up-regulation of HvVRN1 was not required for inflorescence initiation, but might accelerate subsequent stages of inflorescence development. Similar responses to seed vernalization were also observed in wheat (Triticum aestivum). These data support the hypothesis that VRN1 is induced by cold during winter to promote spring flowering in vernalization-responsive cereals

Developmental regulation of cold hardiness in cereals

An understanding of the genetic regulation of low-temperature (LT) tolerance is a prerequisite for the development of cold tolerant cultivars for high stress regions. The objectives of this study were to determine if LT tolerance genes are developmentally regulated. Low-temperature response curves were determined for spring wheat and barley genotypes grown at 4°C under 8 hour (h) short day (SD) and 20 h long day (LD) photoperiods for various acclimation periods up to 112 days. Final leaf number (FLN) and growth of shoot apex was used to determine the stage of phenological development. Expression of LT tolerance genes was determined by LT50. A delay in transition from the vegetative to the reproductive phase in SD sensitive, non-hardy AC Minto spring wheat and highly SD sensitive Dicktoo barley grown under SD resulted in an increased level and/or longer retention of expression of LT tolerance genes. In vernalization requiring winter genotypes photoperiod response of SD sensitive winter barley and wheat genotypes was reflected in the level of expression of LT tolerance genes beginning in the early stages of vernalization and plant development. A delay in transition to the vegetative stage allowed LT acclimation to continue to colder temperatures under SD compared to LD conditions in photoperiod sensitive genotypes. To determine the interrelationships between the developmental stages and LT gene expression, winter wheat genotypes were LT acclimated at 4°C under SD and LD from 0 to 112 d. Also, three de-acclimation (20C) and re-acclimation cycles were used beginning before and after vegetative/reproductive transition. Development of the SD de-acclimated plants was greatly delayed compared to LD plants as determined by shoot apex development, and this delay was reflected in the ability of SD plants to re-acclimate to much lower temperatures. Results indicated that expression of LT tolerance genes is governed by developmental regimes and plants in the vegetative phase have a much greater ability to LT acclimate than plants in the reproductive phase. These results support the hypothesis that level and duration of expression of LT tolerance genes determine the degree of LT tolerance and that LT tolerance genes are developmentally regulated

E-survey (surveys based on e-mail & web) Analysis and identification of cold responsive proteins in Kohdasht spring wheat (Triticum aestivum)

AbstractSpring wheat is cultivated early in the spring in moderate climatic areas or cultivated late in the winter when freezing period is over. To understand plant’s response to the cold stress, former studies have led researchers to the identification of several proteins either in wheat or in other plants. In order to achieve further information regarding with the mechanism of spring wheat response to the cold stress at protein expression level, proteomics was applied for an Iranian local spring wheat cv. Kohdasht (LT50=−4 to −6∘C). Seedlings were first grown in a controlled growth room at 20∘C for 14 days and subsequently were transferred to 4∘C (experimental day 0) for 42 days (cold treatment), or they were maintained at 20∘C (control treatment). Sampling was done on days 0, 21 and 42 of the cold exposure. Protein extraction was carried out and two dimensional analysis were done. Proteins that showed at least two levels of expression changes were identified and mass spectrometry was carried out for their identification. The study led us to the identification of 92 proteins several of which seem to play important role in plant’s response to the cold stress such as cold regulated protein and ferredoxin-NADP(H) oxidoreductase as well as heat shock protein 70. Here we report proteomics analysis of cold responsive proteins and discuss their role in Kohdasht spring wheat cultivar