Ohara Takashi, Takeuchi Haruki, Sato Junya, Nakamura Atsuko, Ichikawa Hiroaki, Yokoyama Ryusuke, Nishitani Kazuhiko, Minami Eiichi, Satoh Shinobu, Iwai Hiroaki
University of Tsukuba, Faculty of Life and Environmental SciencesTsukuba, Ibaraki 305, 8572Japan.
Institute of Agrobiological Sciences, National Agriculture and Food Research OrganizationTsukuba, Ibaraki 305, 8634Japan.
Plant Cell Physiol. 2021 Sep 24;62(4):641-649. doi: 10.1093/pcp/pcab019.
Pectin, a component of the plant cell wall, is involved in cell adhesion and environmental adaptations. We generated OsPG-FOX rice lines with little pectin due to overexpression of the gene encoding a pectin-degrading enzyme [polygalacturonase (PG)]. Overexpression of OsPG2 in rice under weak light conditions increased the activity of PG, which increased the degradation of pectin in the cell wall, thereby reducing adhesion. Under weak light conditions, the overexpression of OsPG decreased the pectin content and cell adhesion, resulting in abnormally large intercellular gaps and facilitating invasion by the rice blast fungus. OsPG2-FOX plants had weaker mechanical properties and greater sensitivity to biotic stresses than wild-type (WT) plants. However, the expression levels of disease resistance genes in non-infected leaves of OsPG2-FOX were more than twice as high as those of the WT and the intensity of disease symptoms was reduced, compared with the WT. Under normal light conditions, overexpression of OsPG2 decreased the pectin content, but did not affect cell adhesion and sensitivity to biotic stresses. Therefore, PG plays a role in regulating intercellular adhesion and the response to biotic stresses in rice.
果胶是植物细胞壁的一种成分，参与细胞黏附及环境适应性过程。我们通过过表达编码一种果胶降解酶[多聚半乳糖醛酸酶（PG）]的基因，培育出了果胶含量低的OsPG - FOX水稻品系。在弱光条件下，水稻中OsPG2的过表达增加了PG的活性，这导致细胞壁中果胶的降解增加，从而降低了细胞黏附。在弱光条件下，OsPG的过表达降低了果胶含量和细胞黏附，导致细胞间隙异常增大，便于稻瘟病菌侵入。与野生型（WT）植株相比，OsPG2 - FOX植株的机械性能较弱，对生物胁迫更敏感。然而，与WT相比，OsPG2 - FOX未感染叶片中抗病基因的表达水平高出WT两倍多，且病害症状的严重程度降低。在正常光照条件下，OsPG2的过表达降低了果胶含量，但不影响细胞黏附及对生物胁迫的敏感性。因此，PG在调节水稻细胞间黏附及对生物胁迫的响应中发挥作用。
