Importance of amylases for physiological quality in maize seeds

Abstract

ResumoImportância das amilases na qualidade isiológica de sementes de milho. A qualidade de sementes está associada à soma dos atributos genéticos, físicos, isiológicos e sanitários que afetam sua capacidade para realizar as funções vitais, estando relacionada à germinação, ao vigor e à longevidade. A expressão de genes associados à qualidade isiológica pode ser avaliada por meio de análises de germinação e vigor, e ainda pelas análises de transcritos e de proteínas em sementes. Objetivou-se com este trabalho fazer uma revisão sobre a relevância das enzimas do grupo das amilases relacionadas à qualidade isiológica de sementes de milho. Dentro do grupo das amilases, a α-amilase (1,4-α-D-glucan-glucanohydrolase, E.C 3.2.1.1) é uma enzima importante na hidrólise do amido, sendo responsável por 90% da atividade amilolítica em sementes de milho. Essa enzima, a exemplo da dextrose, causa a conversão de amido em açúcares que são utilizados no crescimento do embrião. Já a β-amilase (1,4-α-D-glucan maltohydrolase, E.C 3.2.1.2) catalisa a liberação de maltose e dextrinas a partir das extremidades não redutoras do amido. Pesquisas comprovam que as enzimas amilases estão ligadas diretamente à qualidade isiológica de sementes de milho. A α-amilase e a β-amilase estão envolvidas principalmente no processo de germinação e na heterose das sementes, podendo ser também utilizadas como marcadores moleculares relacionadas à tolerância de secagem das sementes.Palavras-chave: α-amilase; β-amilase; Germinação; Heterose; Marcador molecular AbstractSeed quality is the result of the sum of genetic, physical, physiological and sanitary attributes that affect seed ability to perform vital functions related to germination, vigor, and longevity. The expression of genes associated with physiological quality can be assessed by means of germination and vigor analyses, as well as by transcript and protein analyses. The objective in this work was to review the relevance of amylase group enzymes to the physiological quality of maize seeds. Within this group, α-amylase (1,4-α-D-glucan glucanohydrolase E.C 3.2.1.1) plays an important role in starch hydrolysis, and is responsible for 90% of the amylolytic activity in maize seeds. It is responsible for starch conversion into sugars (e.g., destrin), which is used for embryo growth. β-amylase (1,4-α-D-glucan maltohydrolase E.C 3.2.1.2) catalyzes the release of maltose and dextrins from the non-reducing ends of starch. Research has shown that amylase enzymes are directly linked to physiological quality of maize seeds. Alpha-and beta-amylases are mainly involved in the germination process and seed heterosis, and can also be used as molecular markers associated with seed tolerance for drying.

Seed reserves reduction rate and reserves mobilization to the seedling explain the vigour of maize seeds

“…Researches on maize in recent years are usually specific for the relationship between physiological quality and the factors that affect it such as storage components (Nerling et al, 2018;Abreu et al, 2016;Coelho, 2016a), enzymes (Oliveira et al, 2015;Santos et al, 2016;Silva-Neta et al, 2015;Lopes et al, 2017;Diniz et al, 2018), heterosis (Nerling et al, 2013;Oliveira et al, 2015;Coelho, 2016a;Coelho, 2016b;Abreu et al, 2018) and image analysis (Pinto et al, 2015;Dias et al, 2015;Castan et al, 2018;Medeiros et al, 2018).…”

Temperatures and periods of drying delay and quality of corn seeds harvested on the ears

“…At 60 ºC, both deterioration and respiration accelerate, with consequent consumption of reserves, protein denaturation and isoenzymic alterations, which overall impair the physiology of seeds (Rangel et al, 2003). Lopes et al (2017) correlate the enzymes α-and β-amylase with seed quality. At high temperatures, they denature, drastically compromising the potential of seed lots, as they are responsible for processes such as the hydrolysis of starch and the catalysis of maltose and dextrins, which are crucial for maintaining the physiological quality of seeds.…”

Tolerance to delay in drying of hybrid maize seeds related to parental line and temperature

“…The α-AM enzyme is important for seed physiological quality because it acts in starch hydrolysis, supplying energy for embryo growth. Variation in temperature affects this enzyme, compromising the physiological quality of maize seeds (Santos et al, 2015;Lopes et al, 2017).…”

“…Hybrid maize seeds exhibited greater expression of the α-AM enzyme (Figure 5); seed physiological quality was greater in the genotypes. However, Lopes et al (2017) emphasize that the physiological quality of maize seeds is related to the genotype. Thus, for some authors, the greater physiological quality that hybrid maize seeds have in relation to the lines is due to the gain in heterosis that the hybrid seeds have (Reis et al, 2011;Oliveira et al, 2013).…”