Michavila Santiago, Encina Antonio, De la Rubia Alfonso G, Centeno María Luz, García-Angulo Penélope
Grupo de Investigación de Fisiología y Biotecnología de Plantas (FISIOVEGEN), Departamento de Ingeniería y Ciencias Agrarias, Facultad de Ciencias Biológicas y Ambientales, Universidad de León, Área de Fisiología Vegetal, Campus de Vegazana s/n, 24071, León, Spain.
Genómica y Proteómica (INBIOMIC), Instituto de Biología Molecular, Universidad de León, Campus de Vegazana s/n, 24071, León, Spain.
Protoplasma. 2025 Feb 18. doi: 10.1007/s00709-025-02041-5.
Pine needles are specialized leaves bearing distinctive anatomical features whose function is to minimize water loss. At the molecular level, needle specialization is expected to lead to heterogeneity in cell wall (CW) composition. By immunohistochemical analysis of CW epitopes in maritime pine (Pinus pinaster) needles, we described the variability of CW composition in all tissues, discussing its possible relationship with the cell function. Cells specialized in water transport, tracheids, transfusion tracheids, and endodermis, together with epi/hypodermal and stomatal cells, had similar CW composition, where epitopes for pectins (homogalacturonan and rhamnogalacturonan-I), xyloglucan, and heteroxylans were abundant. Heteroxylans differ between the dermis, enriched in arabinoxylan, and endodermis, enriched in glucuronoxylan. Xylem CWs were very rich in (arabino)xylans and homogalacturonan and distinctively lacked immunolabelling for rhamnogalacturonan-I. CWs from phloem, transfusion phloem, mesophyll, and resin ducts were enriched in homogalacturonan, rhamnogalacturonan-I, and xyloglucan, showing a low content for heteroxylan epitopes. Arabinogalactan proteins were detected in mesophyll and in cells specialized in solute transport such as phloem, duct sheath, and guard cells. These results show that tissues with similar functions have similar polysaccharide composition, shedding light on the role of CW components through different tissues.
松针是具有独特解剖特征的特化叶片，其功能是尽量减少水分流失。在分子水平上，针叶特化预计会导致细胞壁（CW）组成的异质性。通过对海岸松（Pinus pinaster）针叶中CW表位的免疫组织化学分析，我们描述了所有组织中CW组成的变异性，并讨论了其与细胞功能的可能关系。专门负责水分运输的细胞，如管胞、转输管胞和内皮层，以及表皮/下表皮细胞和气孔细胞，具有相似的CW组成，其中果胶（同型半乳糖醛酸聚糖和鼠李半乳糖醛酸聚糖-I）、木葡聚糖和杂木聚糖的表位丰富。真皮中富含阿拉伯木聚糖，内皮层中富含葡萄糖醛酸木聚糖，二者的杂木聚糖有所不同。木质部CW富含（阿拉伯）木聚糖和同型半乳糖醛酸聚糖，且明显缺乏鼠李半乳糖醛酸聚糖-I的免疫标记。韧皮部、转输韧皮部、叶肉和树脂道的CW富含同型半乳糖醛酸聚糖、鼠李半乳糖醛酸聚糖-I和木葡聚糖，杂木聚糖表位含量较低。在叶肉以及专门负责溶质运输的细胞中检测到阿拉伯半乳聚糖蛋白，如韧皮部、导管鞘和保卫细胞。这些结果表明，具有相似功能的组织具有相似的多糖组成，这为CW成分在不同组织中的作用提供了线索。
