Cell-Specific Suppression of 4-Coumarate-CoA Ligase Gene Reveals Differential Effect of Lignin on Cell Physiological Function in Populus

Abstract

Lignin is a main component of the secondary cell wall in vessels and fibers of xylem tissue. However, the significance of lignin in cell physiology during plant growth is unclear. In this study, we generated lignin-modified Populus via cell-specific downregulation of the 4-coumarate-CoA ligase gene ( 4CL ). The transgenic plants with selective lignin modification in vessel elements or fiber cells allowed us to investigate how lignin affects the physiology of vessel or fiber cells in relation to plant growth. Results showed that vessel-specific suppression of lignin biosynthesis resulted in deformed vessels and normal fibers, while fiber-specific suppression of lignin biosynthesis led to less-lignified fibers and normal vessels. Further analyses revealed that the efficiency of long distance water transport was severely affected in transgenics with vessel-specific lignin modification, while minimal effect was detected in transgenics with fiber-specific lignin modification. Vessel-specific lignin reduction led to high susceptibility to drought stress and poor growth in field, likely due to vessel defects in long distance transport of water. The distinct physiological significance of lignin in different cell types provides insights into the selective modification of lignin for improvement of lignocellulosic biomass utilization.

Sulfur-Induced Resistance against Pseudomonas syringae pv. actinidiae via Triggering Salicylic Acid Signaling Pathway in Kiwifruit

“…When pathogens infect the plants, they often cause rapid lignification of the infected parts, which implies that lignin analogs are produced and can accumulate in the different parts such as the cell wall, intercellular layer, and the cytoplasm, which can prevent or delay the growth of pathogens and form a physical obstacle for the pathogen infection. Lignin biosynthesis can also play an important role in the long-distance transport of water, a process critical to plant survival [ 58 ]. The PAL gene is the key gene in lignin and phenolic compounds synthesis [ 59 ], and it is closely related to the expression of system acquired resistance [ 60 ].…”

Growth–defense trade‐offs and yield loss in plants with engineered cell walls

“…The expression of a steroid hormone‐inducible COUMAROYL SHIKIMATE 3′‐HYDROXYLASE ( C3′H ) in the Arabidopsis thaliana reduced epidermal fluorescence 8 ( ref8 / c3′h ) mutant greatly alleviated the growth inhibition by permitting the deposition of normal xylem to restore water transport (Kim et al ., 2014). Vessel‐specific expression of CAFFEOYL SHIKIMATE ESTERASE ( CSE ) or CINNAMOYL COA REDUCTASE 1 ( CCR1 ) in A. thaliana cse or ccr1 mutants led to recovery of vascular collapse and an increase in total stem biomass (Vargas et al ., 2016; De Meester et al ., 2018), and targeting lignin reduction to fibers in poplar alleviated the growth reductions observed if the lignin modification were allowed to occur in vessels (Cao et al ., 2020; Gui et al ., 2020). Lignin biosynthetic mutants in Medicago truncatula showed defects in vascular integrity (Nakashima et al ., 2008; Ha et al ., 2019).…”

Investigating the Mechanism of Unilateral Cross Incompatibility in Longan (Dimocarpus longan Lour.) Cultivars (Yiduo × Shixia)

“…This is relatable to the known fact that a massive cell wall deposition is required for fast elongation of pollen tubes, and that we observed faint pollen tube signals in YS24 (Figure 2). Earlier studies explained that the deposition of lignin was affected by changes in the expression of 4CLs and CA3OM (Ma and Xu, 2008;Cao et al, 2020). Thus, these genes would be a suitable candidate for increasing lignin deposition in elongating pollen tubes.…”