Abstract

Lettuce, Lactuca sativa, is one of the main leafy vegetable crops, interesting as a source of phytonutrients. It is extensively studied for biotechnological applications based on in vitro regeneration. However, in lettuce, histological studies of adventitious morphogenesis during the regeneration process are lacking. Analogously, the genes involved in the initiation of adventitious shoots or embryos are unknown. Here, we used cotyledon explants of a cos lettuce (‘Romana’) to define the histological events of in-vitro morphogenesis at different times, and to investigate the nature of the regeneration pathway. Furthermore, we isolated three homeobox genes, LsWUSCHEL1-LIKE (LsWUS1L), LsWUS2L, and LsSHOOT MERISTEMLESS1-LIKE (LsSTM1L), to evaluate their transcription activity during the ontogenesis of the adventitious structures. De novo morphogenesis quickly proceeded through embryogenic and organogenic pathways, with some developmental abnormalities. The expression of LsWUS1L gradually increased during the in vitro culture of cotyledon explants. Remarkably, we detected high expression of both LsWUS2L and LsSTM1L genes after four days of culture, when the very early stages of morphogenesis were only noticeable through histological analysis. These findings suggest a key role of these genes in the rapid recruitment of the founder cells of adventitious structures.

摘要

莴苣（Lactuca sativa）是主要的多叶蔬菜作物之一，作为植物营养素的来源而备受关注。对于基于体外再生的生物技术应用进行了广泛的研究。然而，在莴苣中，缺乏再生过程中不定形态发生的组织学研究。类似地，不定芽或胚的起始所涉及的基因是未知的。在这里，我们使用了莴苣的子叶外植体（“ Romana”）来定义不同时间体外形态发生的组织学事件，并研究了再生途径的性质。此外，我们分离了三个同源盒基因LsWUSCHEL1-LIKE（LsWUS1L），LsWUS2L，和LsSHOOT MERISTEMLESS1 - LIKE（LsSTM1L），以不定结构的个体发育过程中评估其转录活性。从头形态发生迅速通过胚胎发生和器官发生途径进行，并伴有一些发育异常。在子叶外植体的体外培养过程中，LsWUS1L的表达逐渐增加。值得注意的是，我们检测到LsWUS2L和LsSTM1L的高表达在培养四天后，只有通过组织学分析才能观察到形态发生的非常早期时，才发现这些基因。这些发现表明这些基因在不定结构的始祖细胞的快速募集中起关键作用。