Abstract
Alpha-amylase, the major form of amylase with secondary carbohydrate binding sites, is a crucial enzyme throughout the growth period and life cycle of angiosperm. In rice, alpha-amylase isozymes are critical for the formation of the storage starch granule during seed maturation and motivate the stored starch to nourish the developing seedling during seed germination which will directly affect the plant growth and field yield. Alpha-amylase has not yet been studied intensely to understand its classification, structure, expression trait, and expression regulation in rice and other crops. Among the 10-rice alpha-amylases, most were exclusively expressed in the developing seed embryo and induced in the seed germination process. During rice seed germination, the expression of alpha-amylase genes is known to be regulated negatively by sugar in embryos, however positively by gibberellin (GA) in endosperm through competitively binding to the specific promoter domain; besides, it is also controlled by a series of other abiotic or biotic factors, such as salinity. In this review, we overviewed the research progress of alpha-amylase with focus on seed germination and reflected on how in-depth work might elucidate its regulation and facilitate crop breeding as an efficient biomarker.
Highlights
Rice is a staple food for more than half of the world’s population
Double fertilization results in a diploid embryo and a starchy triploid endosperm, with the embryo consisting of an embryonic axis surrounded by a single cotyledon called scutella
For the endosperm-dominant rice seeds, the embryo makes up roughly 2% of the total dry weight of the seed while the endosperm accounts for 98% of the total dry weight of which 87.8% is the starchy endosperm [30]
Summary
Rice seeds are enriched with starch, proteins, and lipids. Double fertilization results in a diploid embryo and a starchy triploid endosperm, with the embryo consisting of an embryonic axis surrounded by a single cotyledon called scutella. Only the embryo and aleurone are alive in the matured seed [1]. A clear relationship was found between the enzyme activity of alpha-amylase (EC 3.2.1.1) and starch content in the leaf sheath after heading with the activity being. DThsetaarcchugmraunlautleeds satraercahssienmmbaletudrbinygssmeeadllsereqstuairpcshtghreamnuwleitshinthtoe 1su0–ff2i0cieμnmt spuabrstitcrlaetses[1f0o,r11s]e.eTdhgeearmcciunmatuiolant.ed starch in maturing seeds equips them with the sufficient substrates for seed germination. Sucrose is rapidly consumed by the growing embryonic axis. OInaonudr dpermevoinosutsrastetuddtyh,atwtehedleetveecltsedofoitnseporof ttehine aanlpdhma-RamNAylabsoeth(asmigynliafiscea1nAtl)yiinnctrheeasreicaensdeepdeaekmabt r4y8oHaAnId dduerminogngsterramteidnatthiaotnth[2e9l]e, vwehlsicohf iitns apdrdotietiionnatnoditms RreNspAonbositvhesniegsnsiftiocapnhtylytoinhcorremasoenaens,dmpaeyakdeatte4r8mHinAeI tdheursitnagrcghegrmrainnualteiotnra[n2s9f]o,rwmhaitciohnininatdhdeitgioernmtoiniattsinregspriocenssieveedn.ess to phytohormones, may determine the starch granule transformation in the germinating rice seed Styhnethaelesuisroofnβe-alamyyelrasaenodccthuerseopnitlyheinliathl elaayleeur.roInne oluayreprr,ewvihoiulestshtautdoyf, walpe hdae-taemctyedlasoenoecocfutrhsebaoltphhian-athmeyalalesuer(oanmeyllaasyee1rAa)nidn tthhee reipciethseeleidalelmayberry. oInaonudr dpermevoinosutsrastetuddtyh,atwtehedleetveecltsedofoitnseporof ttehine aanlpdhma-RamNAylabsoeth(asmigynliafiscea1nAtl)yiinnctrheeasreicaensdeepdeaekmabt r4y8oHaAnId dduerminogngsterramteidnatthiaotnth[2e9l]e, vwehlsicohf iitns apdrdotietiionnatnoditms RreNspAonbositvhesniegsnsiftiocapnhtylytoinhcorremasoenaens,dmpaeyakdeatte4r8mHinAeI tdheursitnagrcghegrmrainnualteiotnra[n2s9f]o,rwmhaitciohnininatdhdeitgioernmtoiniattsinregspriocenssieveedn.ess to phytohormones, may determine the starch granule transformation in the germinating rice seed
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