Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

mRNA FINGERPRINTING DURING ACQUISITION OF TOLERANCE TO LOW TEMPERATURE AT GERMINATION IN MAIZE

CASARINI E., FRASCAROLI E., CONTI S.

Dipartimento di Scienze e Tecnologie Agroambientali, Universita' di Bologna, Via Filippo Re 6, Bologna Italy

cold tolerance, germination, maize, defoliation, gene expression, cDNA-AFLP

Selection of maize with the ability of germinate and growth in cold soils is an important objective for breeders in temperate regions. Early sowing allows to better exploit the growing season length, with important agronomic advantages. A main constraint to successfully apply this practice is the susceptibility of this crop to cold stress during seed germination. It has been evidenced that defoliation during kernel maturation can improve, in responsive genotypes, cold tolerance of germinating seeds and, besides, of embryos rescued few days after defoliation. This latter finding suggests that defoliation does not affect merely kernel maturation, but it possibly acts also on genes involved in acquisition of cold tolerance.

Objective of this study is to assess gene expression that follow defoliation and that corresponds to the acquisition of cold tolerance. Two inbred lines (Lo1016 and Lo964) were grown in field condition and plants were selfed. Approximately 450 growing degree units (25 days) after pollination, half of the plants of each inbred line were completely defoliated. Samples of ears of defoliated (D) or non defoliated (ND) plants were harvested 0, 1, 2, 3, 4, 5 days after the treatment, embryos were rescued and germinated in vitro at cold (9°C) or control (25°C) condition. Results indicated that defoliation did improve embryo germinability at low temperatures of Lo1016 starting from two days after the treatment, while did not affect those of Lo964. A sample of non germinating embryos of D and ND ears was also collected at each time for gene expression analysis. RNA was extracted from tissues and cDNA-AFLP protocol was applied. Expression patterns differing among the two inbred lines, the two defoliation treatments, and associated to the different genotypic response to defoliation, were identified. Transcription derived fragments (TDFs) were cloned, sequenced and compared with nucleotide and amino-acid sequences from databases. Some of them showed similarities with sequences belonging to proteins possibly involved in the cold tolerance (Alcohol- dehydrogenase, ABA induced proteins). Other TDFs showed homology with cDNA sequences obtained from immature embryos, kernels, radicles of maize germinating seeds.