Extracellular matrix and wall composition are diverse in the organogenic and non-organogenic calli of Actinidia arguta

Abstract

Key message Differences in the composition and the structural organisation of the extracellular matrix correlate with the morphogenic competence of the callus tissue that originated from the isolated endosperm of kiwifruit. Abstract The chemical composition and structural organisation of the extracellular matrix, including the cell wall and the layer on its surface, may correspond with the morphogenic competence of a tissue. In the presented study, this relationship was found in the callus tissue that had been differentiated from the isolated endosperm of the kiwiberry, Actinidia arguta. The experimental system was based on callus samples of exactly the same age that had originated from an isolated endosperm but were cultured under controlled conditions promoting either an organogenic or a non-organogenic pathway. The analyses which were performed using bright field, fluorescence and scanning electron microscopy techniques showed significant differences between the two types of calli. The organogenic tissue was compact and the outer walls of the peripheral cells were covered with granular structures. The non-organogenic tissue was composed of loosely attached cells, which were connected via a net-like structure. The extracellular matrices from both the non-and organogenic tissues were abundant in pectic homogalacturonan and extensins (LM19, LM20, JIM11, JIM12 and JIM20 epitopes), but the epitopes that are characteristic for rhamnogalacturonan I (LM5 and LM6), hemicellulose (LM25) and the arabinogalactan protein (LM2) were detected only in the non-organogenic callus. Moreover, we report the epitopes, which presence is characteristic for the Actinidia endosperm (LM21 and LM25, heteromannan and xyloglucan) and for the endosperm-derived cells that undergo dedifferentiation (loss of LM21 and LM25; appearance or increase in the content of LM5, LM6, LM19, JIM11, JIM12, JIM20, JIM8 and JIM16 epitopes).

Cell Wall Composition as a Marker of the Reprogramming of the Cell Fate on the Example of a Daucus carota (L.) Hypocotyl in Which Somatic Embryogenesis Was Induced

“…The epitope that is recognized by the LM20 antibody was present in all of the explant cell walls prior to their transfer to the induction medium as well as during the culture. No changes were observed in the occurrence of this epitope between the different explant cell types or culture time points, thus indicating that highly esterified pectins are an essential component of the cell walls of an explant, which is consistent with the literature data ( [55] and literature therein). It also indicates that this epitope is not a marker of any changes in the cell reprogramming for the carrot hypocotyl explant during the induction phase of SE.…”

“…A similar pattern of the distribution of this epitope has been observed in the actively dividing cells during Triticum aestivum organogenesis [41]. In the embryogenic callus of Brachypodium, this epitope was detected in the embryogenic cells [30] and during the SE of T. nigresens [31], however, in the Arabidopsis explant [54] and in Actinidia arguta [55], it was not detected in the cells that were changing their fate. The results indicate that during the induction phase in a carrot explant, this epitope can be considered to be a marker of the cells that are reprogramming their fate.…”

“…Namely, cytological features such as dense cytoplasm, a high nucleus/cytoplasm ratio, an isodiametric cell shape, a spherically shaped nucleus with one or more nucleoli, small vacuoles, and thin cell walls are characteristics of pluripotent cells ( [56] and literature therein). Such features have been observed in cells of different origins during the acquisition of embryogenic potential ( [9,[54][55][56]77] and literature therein). In the studies presented here, the changes in the cell wall composition were related to the observed cytological features for the cells that were undergoing reprogramming.…”

“…In the present work, only the epitope that is recognized by JIM11 can be postulated as being a marker of the detached cells. In the Brachypodium callus [30] and in the Actinidia arguta callus [55], this epitope was detected in the intercellular spaces. This result may indicate the involvement of extensins in increasing the strength of the walls, which was also found, among others, by Knox [19].…”

“…It is postulated that the JIM4 epitope may be a marker for all of the stages accompanying the acquisition of embryogenic state by cells during carrot SE [39]. The non-methyl esterified (LM19) and methyl-esterified (LM20) HG together with LM5, LM6, JIM11, JIM12, JIM8, and JIM16 epitopes were described as characteristic for endosperm-derived cells that undergo dedifferentiation during the Actinidia arguta culture in vitro [55]. It has also been shown that the pectic epitope that is recognized by the LM8 antibody was absent, regardless of the morphogenic capacity of the Actinidia arguta callus [55].…”