College of Forestry, Northwest A&F University, Yangling, Shaanxi, 712100, China.
Research Centre for Jujube Engineering and Technology of State Forestry and Grassland Administration, Key Comprehensive Laboratory of Forestry of Shaanxi Province, Northwest A&F University, Yangling, Shaanxi, 712100, China.
BMC Plant Biol. 2024 Nov 4;24(1):1041. doi: 10.1186/s12870-024-05760-8.
Chinese jujube (Ziziphus jujuba Mill.), also called Chinese date, is one of the oldest and widely cultivated fruit trees with great economic values, which, at least, can be attributed to the melliferous flower with highly developed nectary that can secret huge amount of nectar in a rather tiny floral size. However, the morphological nature, metabolic products, developmental process, as well as molecular and regulatory mechanisms of jujube nectary remain largely unknown.
Here, we selected Z. jujuba 'Dongzao' as a system to address these questions. We uncovered that the jujube nectary is an annular or donut-shaped secretory protrusion that surrounds the base of the carpels, along with emerald and glistening hues, which can produce a bulk honey with many metabolic compounds (e.g. saccharides and flavonoids) that has a high nutritional value and benefit for human health. The development of jujube nectary is a dynamic process of earlier cell division followed by later cell expansion. We also identified putative genes associated with the nectary development and found that the CRABS CLAW (CRC) ortholog (ZjCRC) is the key to nectary development: the gene is highly expressed in nectary; ectopic expression of it in the Arabidopsis crc-1 mutant rescued the lost nectary (also the carpel and silique defects). We also demonstrated that a MADS-box transcription factor ZjAGAMOUS1 (ZjAG1) is required for the direct activation of ZjCRC expression.
Taken together, our results not only provide a comprehensive portrait of the jujube nectary, but also pave the way to effective utilization of jujube and other woody crops.
大枣（Ziziphus jujuba Mill.），又称中国枣，是最古老和广泛种植的果树之一，具有巨大的经济价值，这至少可以归因于其花蜜丰富，具有高度发达的蜜腺，在相当小的花部尺寸中能分泌大量的花蜜。然而，大枣蜜腺的形态发生、代谢产物、发育过程以及分子和调控机制在很大程度上仍不清楚。
在这里，我们选择‘冬枣’（Z. jujuba 'Dongzao'）作为系统来解决这些问题。我们揭示了大枣蜜腺是一种环绕心皮基部的环形或甜甜圈形分泌突起，呈现出翠绿色和晶莹剔透的色泽，可以产生具有高营养价值和有益于人类健康的大量代谢化合物（如糖和类黄酮）的蜂蜜。大枣蜜腺的发育是一个早期细胞分裂随后是后期细胞扩张的动态过程。我们还鉴定了与蜜腺发育相关的假定基因，并发现 CRABS CLAW（CRC）同源物（ZjCRC）是蜜腺发育的关键：该基因在蜜腺中高度表达；在拟南芥 crc-1 突变体中外源表达它挽救了丧失的蜜腺（以及心皮和蒴果缺陷）。我们还证明了一个 MADS-box 转录因子 ZjAGAMOUS1（ZjAG1）是直接激活 ZjCRC 表达所必需的。
综上所述，我们的结果不仅提供了大枣蜜腺的全面描述，也为大枣和其他木本作物的有效利用铺平了道路。
