Laboratori del Suro, Departament de Biologia, Universitat de Girona, Campus Montilivi, 17003, Girona, Spain.
Sci Rep. 2021 Jun 8;11(1):12053. doi: 10.1038/s41598-021-90938-5.
The phellogen or cork cambium stem cells that divide periclinally and outwardly specify phellem or cork. Despite the vital importance of phellem in protecting the radially-growing plant organs and wounded tissues, practically only the suberin biosynthetic process has been studied molecularly so far. Since cork oak (Quercus suber) phellogen is seasonally activated and its proliferation and specification to phellem cells is a continuous developmental process, the differentially expressed genes during the cork seasonal growth served us to identify molecular processes embracing from phellogen to mature differentiated phellem cell. At the beginning of cork growth (April), cell cycle regulation, meristem proliferation and maintenance and processes triggering cell differentiation were upregulated, showing an enrichment of phellogenic cells from which phellem cells are specified. Instead, at maximum (June) and advanced (July) cork growth, metabolic processes paralleling the phellem cell chemical composition, such as the biosynthesis of suberin, lignin, triterpenes and soluble aromatic compounds, were upregulated. Particularly in July, polysaccharides- and lignin-related secondary cell wall processes presented a maximal expression, indicating a cell wall reinforcement in the later stages of cork formation, presumably related with the initiation of latecork development. The putative function of relevant genes identified are discussed in the context of phellem ontogeny.
栓内层或软木形成层干细胞通过平周分裂和向外分裂指定栓内层或软木。尽管栓内层在保护径向生长的植物器官和受伤组织方面至关重要，但迄今为止，实际上仅研究了木质素的生物合成过程。由于栓皮栎（Quercus suber）栓内层具有季节性激活的特性，其增殖和特化为栓内层细胞是一个连续的发育过程，因此在栓皮季节性生长过程中差异表达的基因可用于鉴定从栓内层到成熟分化的栓内层细胞的分子过程。在栓皮开始生长（四月）时，细胞周期调控、分生组织增殖和维持以及触发细胞分化的过程上调，表明从栓内层中特异性地出现了栓内层细胞。相反，在栓皮生长的高峰期（六月）和后期（七月），与栓内层细胞化学成分平行的代谢过程上调，如木质素、三萜、类黄酮和可溶性芳香族化合物的生物合成。特别是在七月，与多糖和木质素相关的次生细胞壁过程表达达到最大值，表明在栓皮形成的后期阶段细胞壁得到了加强，可能与晚期栓皮发育的启动有关。讨论了鉴定的相关基因的可能功能，这些基因的功能是在栓内层发生的背景下讨论的。
