CELLULASE 6 and MANNANASE 7 affect cell differentiation and silique dehiscence

Cellulases (纤维素酶), hemicelluloses (半纤维素酶) and pectinases (果胶酶) play important roles in fruit development and maturation. Although mutants with defects in these processes have not been reported for cellulase or hemicellulase genes, the pectinases ARABIDOPSIS DEHISCENCE ZONE POLYGALACTURONASE 1 (ADPG1) and ADPG2 were previously shown to be essential for silique dehiscence (角果开裂) in Arabidopsis. Here we demonstrate that the cellulase gene CELLULASE 6 (CEL6) and the hemicellulase gene MANNANASE7 (MAN7) function in the development and dehiscence of Arabidopsis thaliana siliques. We found that these genes were expressed in both vegetative and reproductive organs, and that their expression in the silique partially depended on the INDEHISCENT (IND) and ALCATRAZ (ALC) transcription factors. Cell differentiation (细胞分化) was delayed in the dehiscence zone of cel6 and man7 mutant siliques at early flower development stage 17, and a comparison of the spatio-temporal patterns (时空模式) of CEL6 and MAN7 expression with the locations of delayed cell differentiation in the cel6 and man7 mutants revealed that CEL6 and MAN7 likely indirectly affect the timing of cell differentiation in the silique valve at this stage. CEL6 and MAN7 were also found to promote cell degeneration in the separation layer (离层) in nearly mature siliques, as cells in this layer remained intact in the cel6 and man7 mutants and the cel6-1man7-3 double mutant, whereas they degenerated in the wild-type control. Phenotypic studies of single, double, triple and quadruple mutants revealed that higher-order (高阶) mutant combinations of cel6-1, man7-3, and adpg1-1 and adpg2-1 produced more severe silique indehiscent (不裂) phenotypes than the corresponding lower-order mutant combinations, except for some combinations involving cel6-1, man7-3, and adpg2-1. Our results demonstrate that the ability of the silique to dehisce can be manipulated to different degrees by altering the activities of various cell wall modifying enzymes.

纤维素、半纤维素和果胶酶在果实发育和成熟过程中发挥重要作用。尽管纤维素和半纤维素对于果实发育和成熟过程的突变缺陷并未有过报道，然而果胶酶ADPG1和ADPG2在先前的报道中被证明参与了拟南芥的角果开裂。本文报道了纤维素酶编码基因CEL6和半纤维素酶编码基因MAN7作用于拟南芥角果的发育和开裂。作者发现这些基因在营养和生殖器官中均表达，并且它们在角果中的表达部分依赖于转录因子IND和ALC。在早期花发育阶段17时，突变体cel6和man7的角果细胞分化有延迟，通过比较CEL6和MAN7基因时空表达模式和cel6和man7突变体中的延迟细胞分化的位置显示CEL6和MAN7可能间接影响角果在该时期细胞分化的时间。作者还发现CEL6和MAN7在靠近成熟角果的离层组织中会促进细胞的退化，当野生型该处组织的细胞已经退化时，在cel6和man7突变体以及cel6-1man7-3双突变体中该处组织的细胞仍然保持完整。通过单突、双突、三突及四突显示，出了含有cel6-1、man7-3和adpg2-1这三个突变的组合，所有的cel6-1、man7-3、adpg1-1和adpg2-1高阶突变组合较对应的低阶突变组合会产生更加严重的角果不裂表型。本文的研究显示可以通过改变不同细胞壁修饰酶的活性来获得不同程度的角果开裂表型。

通讯：吴鸿 (http://life.scau.edu.cn/nav-staff-30001298.asp)

个人简介：1980-1984年，西北大学，学士，方向：药用植物学；1984-1987年，西北大学，硕士，方向：植物学；1991-1994年，西北大学，博士，方向：植物学。

doi: https://doi.org/10.1104/pp.17.01494