灌浆期遮光对不同粒色小麦籽粒花青素积累与相关酶活性的影响

摘要

To understand the pathway of anthocyanin accumulation during grain filling of wheat (Triticum aestivum L.) and its response to light, we used three red-gain, two black-grain, and one white-grain (control) varieties (lines) to investigate the dynamic changes of anthocyanin accumulation and activities of related enzymes during grain filling. Shadin g treatments were conducted during the whole filling stage (14-34 days post anthesis, treatment T1) and at early (14-24 d post anthesis, treatment T2)or late filling stage (24-34 days post anthesis, treatment T3), and natural light condition without shading was used as the control.The effects of treatments T1 and T3 on anthocyanin content were larger than that of treatment T2, indicating that late grain filling period is critical for anthocyanin biosynthesis. The changing degree of anthocyanin content induced by shading varied across varieties with larger changes in D4 Hong (red grain), Hong 5 (red grain), and Heixiaomai 76 (purple red grain). In the treatment T1,the grains of three red-grain varieties with anthocyanin content less than 1 U g-1 were colorless, similar to the white-grain control "Jimai 19". In the treatment T2, the anthocyanin began to be synthesised after the shading was removed in late grain filling period.The anthocyanin contents of black-grain wheat varieties Changyi Heimai and D4 Hei were significantly reduced in shading treatments, but the absolute content was higher than 2 U g-1 in the treatment T1. This result suggested different pathways of anthocyanin biosynthesis probably light-dependent in red-grain wheat. While both light-dependent and non-light-dependent pathways in black-grain wheat,of which the latter was the main pathway .In colored-grain wheat,the activities of plenylalanine ammonialyase(PAL) and chalcone ismoerase(CHI)were low in early grain-filling period,and increased to a higher level in middle to late filling period.However,the activity of polyphenol oxidase(PPO)varied from a high level in early filling period to a low level in middle to late filling period.In the control treatment without shading,the activities of PAL and CHI were positively associated with anthocyanin content at a significant level.indicating that CHI and PAL are the key enzymes in anthocyanin biosynthesis.The PPO activity was negatively correlated with anthocyanin content in black-grain wheat rather than red-grain wheat Under the shading conditions,the activities of PAL,CHI ,and PPO were not closely associated with the anthocyanin content Therefore,it is inferred that the effect of light on anthocyanin biosynthesis not based on the direct regulations of PAL.CHI,and PPO activities.%为探讨光照条件对不同粒色小麦籽粒花青素合成与积累的影响,以红粒小麦品种(系)D4红、红5、黑小麦76,黑粒小麦品系D4黑、昌邑黑麦,以及普通小麦济麦19(白粒)为材料,研究穗部遮光对不同粒色小麦籽粒发育过程中花青素积累及相关酶活性的影响.全灌浆期穗部遮光或后期遮光对籽粒花青素含量的影响显著大于前期遮光,说明籽粒灌浆后期是花青素合成的关键时期.穗部遮光对D4红、红5及黑小麦76籽粒花青素含量的影响显著大于黑粒小麦昌邑黑麦与D4黑.3个红粒品种(系)全灌浆期遮光后籽粒花青素含量不足1 U g-1,与白粒品种类似,而前期遮光后期恢复光照后籽粒花青素迅速合成.与未遮光的对照比较,遮光对2个黑粒小麦品系花青素含量影响虽达显著水平,但遮光后黑粒品系花青素含量仍在2 U g-1以上.说明黑粒与红粒小麦籽粒花青素的合成途径不同.红粒小麦的花青素合成可能是一种依赖光的合成途径,而黑粒小麦中可能是依光型和非依光型两种合成途径,且后者是其主要途径.有色小麦籽粒的苯丙氨酸解氨酶(PAL)和查尔酮异构酶(CHI)活性变化趋势是灌浆前期低,中后期高,而多酚氧化酶(PPO)活性则呈前期高,中后期低的变化趋势.未遮光处理的有色小麦,其不同时期籽粒花青素含量与PAL和CHI活性变化趋于一致,且呈显著正相关,表明CHI与PAL是有色小麦籽粒花青素合成的关键酶.黑粒小麦的花青素含量与PPO活性呈显著负相关,而红粒的相关性不显著.遮光后籽粒的花青素含量变化与酶活性变化趋势不一致,说明光照条件对籽粒花青素合成的影响并非直接通过3种酶活性的变化而起作用.