Autumn dormancy regulates the expression of cas18, vsp and corF genes during cold acclimation of lucerne (Medicago sativa L.)

Abstract

As a global forage legume, lucerne (alfalfa, Medicago sativa L.) is valuable for studying the evolutionary and ecological mechanisms of plant adaptation to freezing, owing to the characteristic of contrasting winter hardiness induced by autumn dormancy. Autumn-dormant lucerne plants often exhibit greater cold tolerance than non-dormant plants under natural field conditions. The study examined the autumn shoot growth of four diverse lucerne cultivars, and the influence of two sampling dates in late autumn, three sampling positions and four autumn-dormancy categories on cas18, vsp and corF gene transcripts during the first year of lucerne establishment. Results showed that in field-grown lucerne, non-dormant and highly non-dormant cultivars had greater shoot growth than a dormant cultivar in autumn. The level of transcripts of cas18 (which encodes a dehydrin-like protein) was highest in dormant cultivars and lowest in semi-dormant cultivars in both November and December; in particular, the cas18 transcripts in the crown remained highest in both November and December. The level of transcripts of vsp (which encodes vegetative storage protein) in all dormant cultivar tissues was highest in both November and December. In semi-dormant cultivars, the expression of vsp in the taproot increased compared with the lateral root and crown in November. The corF transcript in the dormant cultivar was markedly higher than in the semi-dormant cultivar and almost zero in the non-dormant and highly non-dormant cultivars. These results indicate that the significant impact of autumn dormancy and plant position on gene expression of cas18, vsp and corF occurring during autumn hardening, and continuing low temperatures, are likely to have significant consequences on lucerne productivity and its long-term persistence.

Metabolomic analyses reveal substances that contribute to the increased freezing tolerance of alfalfa (Medicago sativa L.) after continuous water deficit

“…1, the aboveground parts were separated from below-ground parts, and then each part was washed with water and surfacedried by blotting with filter paper. We collected crowns within approximately 5-cm below ground as described in previous studies [24][25][26]. The crown samples were cut into three segments in preparation for the freezing tolerance test, metabolomics assays, and other analyses, and two out of three segments were frozen at − 80°C until used.…”

Response of Alfalfa (Medicago sativa L.) to Abrupt Chilling as Reflected by Changes in Freezing Tolerance and Soluble Sugars

“…When temperatures increase, the acquired cold resistance of alfalfa is lost through the process of deacclimation [6]. Nevertheless, the contents of cryoprotectant substances are much lower before cold acclimation (in early autumn) or after deacclimation (in late spring) [7][8][9]; at such stages, alfalfa is likely to be killed by frost [1]. Cold-resistant cultivars generally show low fall dormancy [10].…”

“…Cold-resistant cultivars generally show low fall dormancy [10]. To increase winter survivability, cultivars differing in degree of fall dormancy have been selected for production on the basis of tolerance to extremely low temperatures [9]. Although the ability to cope with abrupt-chilling events should be considered during cultivar selection, field studies for development of relevant assessment strategies are lacking.…”

“…However, raffinose and stachyose are the most effective cryoprotectant sugars for protecting alfalfa [5,19,20]. Changes in soluble protein content are also closely associated with freezing tolerance of cold-acclimated alfalfa; for example, K3-dehydrin, a water-stress-protective protein, can maintain cell membrane integrity under cellular dehydration caused by cold stress [9,18,21].…”

“…The synthesis of these enzymes and other substances associated with alfalfa cold resistance are under direct or indirect genic control [23]. Increased expressions of cold-regulated genes, such as Cas15A [5,24] and Cas18 [9,10], can be induced by low temperature. Cas15A encodes a protein of 14.5 kDa that plays an important role in cold resistance [24].…”