蓝莓表皮蜡质损伤与采后果实软化机理研究

Blueberry is highly demanded by consumers due to its nutritional value and health benefits. Its quality is affected by many factors including mechanical injury. For example, the cuticular waxes of the flesh fruit can be easily damaged during and after harvest. The damage can result in a rapid fruit softening and decay so that fruit quality is deteriorated and shelf life is shorted up to 50-70%. Little is known about how the cuticular waxes on fruit surface affects softening and senescence of blueberry. The aim for the proposed project is to investigate the biochemical and molecular mechanics of cuticular waxes on blueberry postharvest fruit softening. Specifically, our objectives are: (1) Characterize the chemical composition and structure of the waxes, and study the impact of the wax damage on cell walls metabolism; (2) Analyze cell transcriptional changes after waxy injury using high -throughput RNA-Seq and quantitative PCR, and study the effect of wax damage on the gene expression profiles; (3) Define the key genes, especially those genes involved in stress responsive network and fruit ripening network acting on wax damage triggered signal transduction. The proposed study will lay a foundation on how to control fruit softening and extend shelf life for blueberry and other berries, which is critical for the healthy development of the emerging berry industry.

蓝莓营养兼具保健功效，是近年发展最具潜力新型浆果。生产发现，蓝莓鲜果表皮覆盖蜡质层且采后极易损伤，迅速加剧果实软化和衰老，保鲜期缩短50%-60%，品质明显下降，软化腐烂，损失巨大。以往蓝莓采后研究多集中在贮藏保鲜技术和品质等，对果皮蜡质、采后损伤与果实软化衰老研究未见报。蜡质与软化发生的信号转导途径、细胞壁代谢、生理变化本质和分子机理尚不清楚。本项目针对蜡质损伤加剧蓝莓采后果实软化问题，从分析蜡质结构及化学组分入手，研究其损伤对果实细胞壁代谢变化影响和关系；应用高通量RNA-Seq、荧光定量PCR等转录组学和核酸定量技术，研究蜡质损伤后转录活动及调控规律；明确其与软化进程关系；揭示其对信号传导网络和功能基因转录的影响，阐明蜡质损伤加速细胞壁代谢的生理变化；探索软化发生进程的分子机理和调控机制。为控制蓝莓采后软化，延长贮藏保鲜期提供理论基础和应用依据，指导浆果新产业快速发展，意义十分重大。

蓝莓因其丰富营养和保健功效，深受消费者喜爱。角质层蜡质是植物自我防护的第一道屏障。这层蜡质在果实采收、包装和运输时很容易受到损伤。本项目从分析蜡质结构及化学组分入手，研究蜡质损伤与果实采后软化的关系，揭示蓝莓外表皮天然蜡质的存在对果实采后品质保持的重要作用。本项目主要研究结果如下：.1. 采用扫描电镜（SEM）研究了不同品种蓝莓角质层蜡质的化学组分和形态。结果表明，蓝莓果实表面被大量的管状蜡质晶体所覆盖，不同品种蓝莓蜡质形态之间无明显的差异。品种之间蜡质总量相差较大，三萜类化合物和β-二酮是蓝莓外表皮蜡质的主要组分，分别占总蜡质的64.2%和16.4%。熊果酸或齐墩果酸是蓝莓蜡质中含量最高的三萜类物质，因品种而异。.2. 为了研究蓝莓表皮蜡质在采后贮藏过程中的作用，采用蓝丁胶去除蓝莓蜡质，加速了果实的采后失水和腐烂，降低了感官和营养品质，缩短了货架期。蜡质的去除导致贮藏后期果实中非酶抗氧化物质和抗氧化酶活性的迅速下降，加速了活性氧的产生、膜脂过氧化、线粒体膜和质膜的降解破裂。天然蜡质的存在对果实采后品质保持具有重要的作用。.3. 蓝莓表皮天然蜡质的去除加速了采后果实的软化。蜡质的去除诱导了果实细胞壁降解酶活性的提高，降低了细胞壁物质含量。蜡质的去除加速了果胶的溶解和解聚，使细胞壁半纤维素-纤维素微纤丝网络结构变得松弛，更利于细胞壁降解酶的作用。