Programmed cell death during the formation of rhytidome and interxylary cork in roots of Astragalus membranaceus (Leguminosae)

Abstract

Programmed cell death (PCD) plays a critical role throughout the lives of plants, it is regarded as a highly regulated and active process of plant cell death during the times of biotic or abiotic stress. This study aims to provide developmental anatomical characteristics of the interxylary cork formation in the roots of Astragalus. membranaceus var. mongholicus, and to subsequently show cytomorphological evidence that PCD is involved in the development of rhytidome and interxylary cork. The developmental anatomy of rhytidome and interxylary cork of the perennial fresh main root of A. membranaceus var. mongholicus was studied using light microscopy, whereas the PCD in the development of rhytidome and interxylary cork was studied using fluorescence microscopy and transmission electron microscopy. Histologically, it was observed that the parenchyma cells of secondary phloem and xylem in roots recovered their meristematic ability, and later developed into rhytidome and interxylary cork. Cytologically, ultrastructural characteristics such as nucleus malformation, vacuole disappearance, mitochondrial degeneration, and vesicle filling were observed. In roots, the nucleus of the phloem parenchyma cells were terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling (TUNEL)‐positive from the pre‐rhytidome stage to the formation of rhytidome stage and 4′,6‐diamidino‐2‐phenylindole dihydrochloride (DAPI)‐negative during the mature rhytidome stage. The TUNEL assay of the xylem parenchyma cells showed positive characteristics from the early stage of interxylary cork formation to the interxylary cork formation stage, whereas DAPI‐negative characteristics were observed in the mature interxylary cork. Gel electrophoresis showed that DNA cleavage was random. Our results indicated that the formation of the rhytidome and interxylary cork involved the PCD process.

The Making of Plant Armor: The Periderm

“…Typically, once formed, phellem cells radially expand to acquire their final dimensions, accumulate a set of different specialized polar and non-polar soluble compounds and modify their cell walls by depositing lignin and suberin (Figure 5b). As chemical differentiation ends, phellem cells remodel chromatin, express developmental programmed cell death marker genes, degrade their cytoplasm and fragment their DNA, in agreement with programmed cell death (61,70,71,170), and eventually autolyze and dehydrate. The empty space framed by cell walls becomes gas-filled (128).…”

Developmental Programmed Cell Death Involved in Ontogenesis of Dictamnus dasycarpus Capitate Glandular Hairs

“…Multilamellar bodies and double membrane-bound autophagosomes have been associated with PCD processes in several species [ 12 , 13 , 15 , 20 , 35 , 36 ]. In the present study, the multivesicular body in the cytoplasm seemed to fuse with the plasma membrane, releasing vesicles into the buckling cell wall, which was also observed in PCD during floral nectary senescence in I. purpurea [ 16 ], aerenchyma formation in Typha angustifolia leaves [ 37 ], and rhytidome and interxylary cork formation of Astragalus membranaceus [ 38 ] and other plant systems [ 39 ]. Interestingly, the fully developed head cells in the PCD process of D. dasycarpu s were not strongly vacuolated, and various organelles gradually degenerated, mainly in the cytoplasm, indicating non-autolytic PCD [ 33 ].…”

Mass spectrometry imaging links interxylary cork formation with phytochemical distribution inScutellaria baicalensis

“…mongholicus (Bge.) Hsiao (Luo, 1987; Han et al ., 2021). Small interxylary corks could be successively or simultaneously formed at different positions of xylem, and the integration of which contributed to the expansion of interxylary cork.…”