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.