REVISITING THE IMPLICATION OF RAFFINOSE FAMILY OLIGOSACCHARIDE SUGARS IN SEED LONGEVITY POINTS TO A ROLE DURING MATURATION AND NOT STORAGE
Leprince, O.1, Vandecasteele, C.2, Ly Vu, B.1 , Hundertmark, M.1, Righetti, K.1, Gallardo, K.3, Aime, D.3, Prosperi, J.-M.4 and Buitink, J.1
1Institut de Recherche en Horticulture et Semences, INRA, Agrocampus Ouest, Université d’Angers, SFR Quasav, Beaucouzé, France
2Génétique, Physiologie et Système d’élevage, INRA, Castanet-Tolosan, France
3Agroécologie, AgroSup Dijon, INRA, Université Bourgogne Franche-Comté, Dijon, France
4Genetic Improvement and Adaptation of Mediterranean and Tropical Plants, INRA, CIRAD, Montpellier Supagro, Montpellier, France
Contact: Olivier Leprince, Olivier.email@example.com
Legume seeds are particularly well-endowed with raffinose family oligosaccharide (RFO) sugars, which are anti-nutritional compounds for mono-gastric animals. RFO sugars accumulate during the final stages of seed maturation and are metabolized during seed germination. While genetic evidence suggests that RFOs are involved in seed vigor and seedling establishment, their involvement in seed longevity remains elusive. Taking advantage of the wide genetic diversity of Medicago truncatula and its long post-filling phase during which seed longevity is acquired, we examined the relationship between seed longevity and RFO contents. Seed lots of 174 recombinant inbred lines grown in two consecutive years were stored at 60% and 75% RH at 35°C. Viability after storage was not correlated with the contents of total RFO, sucrose/RFO or stachyose, which is the predominant sugar in M. truncatula. For 262 accessions from the core collection of this species survival curves were constructed to determine the P50 values (time of storage to reach 50% survival, determined at 60% RH, 35°C). No correlation was found between P50 and contents of galactinol, sucrose, RFO and sucrose/RFO ratio. In a parallel study, we investigated the link between sugar and protein composition during seed maturation and the acquisition of longevity. Using developmental time series from seeds produced under five environmental conditions (drought stress, heat and cold stress, greenhouse, and optimal conditions), we established that the increase in P50 was highly positively correlated with stachyose (r=0.92), verbascose (r=0.807), total RFO (r=0.885) and Suc/RFO (r=0.77). P50 was also highly correlated with legumin b content (r=0.827). These results indicate that RFO can be used as an indicator of seed maturation and acquisition of longevity. However, they are not the main factor determining the genetic variability of longevity in M. truncatula.