Pectate lyase (PEL) is an endogenous pectin-degrading enzyme that is capable of cleaving α-1,4-glycosidic linkages in demethylated pectin by β-elimination. It is a ubiquitous enzyme in higher plants and is encoded by at least 26, 22, and 14 genes in Arabidopsis, poplar (Populus trichocarpa), and rice, respectively. Although several PECTATE LYASE-LIKE (PLL) genes are considered to play potentially diverse physiological roles in plants, such as being expressed in anthers and pollen, and being involved in fruit softening and development, their molecular mechanism in monocots remains largely unknown.

Recently, researchers from China National Rice Research Institute (CNRRI), Chinese Academy of Agricultural Sciences, Huazhong Agricultural University, Institute of Crop Science, Chinese Academy of Agricultural Sciences and Institute of Microbiology, Chinese Academy of Sciences successfully identified a mutant exhibiting dwarfism and an early-senescence leaf phenotype, termed dwarf and early-senescence leaf1 (del1). Histological analysis showed that the abnormal growth was caused by a reduction in cell number. Further investigation revealed that the decline in cell number in del1 was affected by the cell cycle. Physiological analysis, transmission electron microscopy, and TUNEL assays showed that leaf senescence was triggered by the accumulation of reactive oxygen species. The DEL1 gene was cloned using a map-based approach. It was shown to encode a PEL precursor that contains a PelC domain. DEL1 contains all the conserved residues of PEL and has strong similarity with plant PelC. DEL1 is expressed in all tissues but predominantly in elongating tissues. Functional analysis revealed that mutation of DEL1 decreased the total PEL enzymatic activity, increased the degree of methylesterified homogalacturonan, and altered the cell wall composition and structure. In addition, transcriptome assay revealed that a set of cell wall function- and senescence-related gene expression was altered in del1 plants. This research indicates that DEL1 is involved in both the maintenance of normal cell division and the induction of leaf senescence. These findings reveal a new molecular mechanism for plant growth and leaf senescence mediated by PECTATE LYASE-LIKE genes.

This research was supported by the National Natural Science Foundation of China (Grant No. 31661143006, 91435105, 91535205), National Key Basic Research Program (grant no. 2013CBA014), and the “Science and technology innovation project” of the Chinese Academy of Agriculture Sciences. The research finding has been published in Plant Physiology online on April 28, 2017 (DOI: http://dx.doi.org/10.1104/pp.16.01625). More details are available on the links bellow: http://www.plantphysiol.org/content/early/2017/04/28/pp.16.01625.full.pdf+html