Chiral changes of cortical microtubule orientations in epidermis of sunflower hypocotyls. The effect of blue and red light

Light and developmental processes affect the cortical microtubule (cMT) orientation. The cMT orientation with a special regard to its chirality was analyzed under the outer epidermal cell walls in different regions of sunflower hypocotyls kept in darkness and after irradiation with blue and red light. The results show that the cMT orientation depends on the cell position along hypocotyl, but generally cMTs are oblique. The oblique orientation has defined chirality: either of Z-form (right-handed) or S-form (left-handed). In the lower region of hypocotyls the Z-form dominates. After irradiation of hypocotyls with blue light this domination has been maintained and appeared also in the upper region. In contrast, after irradiation with red light the Z-form domination has not been apparent. It is proposed that in darkness, variations of cMT orientations in the epidermis along the hypocotyl are due to developmental processes, while blue and red light affect the cMT orientation via “shifting” these processes backward and forward, respectively

Wpływ wzrostu modulowanego pH i naprężeniem na układ mikrotubul kortykalnych w epidermie hipokotyla słonecznika

Pojęcie wzrostu organizmów żywych ma dwa główne znaczenia: powiększanie wymiarów komórek i organów, na przykład wydłużanie, oraz powiększanie ilości komórek i ich składników, na przykład wzrost świeżej masy. W niniejszej pracy pojęcie wzrostu jest stosowane w pierwszym znaczeniu. Komórki roślinne posiadają ściany komórkowe, dlatego też ich wzrost wymaga powiększania ściany czyli jej odkształcania. To zachodzi tylko wtedy, gdy ściana jest naprężona, czyli działają na nią siły, i to w stopniu takim, że do odkształcenia elastycznego czyli odwracalnego, dodaje się odkształcenie plastyczne - nieodwracalne. Odkształcenie elastyczne jest wprost proporcjonalne do naprężenia, a jego szybkość jest stała. Natomiast zależność odkształcenia plastycznego od naprężenia nie jest liniowa, a szybkość odkształcenia plastycznego zależy od czasu

Does Shoot Apical Meristem Function as the Germline in Safeguarding Against Excess of Mutations?

A genetic continuity of living organisms relies on the germline which is a specialized cell lineage producing gametes. Essential in the germline functioning is the protection of genetic information that is subjected to spontaneous mutations. Due to indeterminate growth, late specification of the germline, and unique longevity, plants are expected to accumulate somatic mutations during their lifetime that leads to decrease in individual and population fitness. However, protective mechanisms, similar to those in animals, exist in plant shoot apical meristem (SAM) allowing plants to reduce the accumulation and transmission of mutations. This review describes cellular- and tissuelevel mechanisms related to spatio-temporal distribution of cell divisions, organization of stem cell lineages, and cell fate specification to argue that the SAM functions analogous to animal germline

Orientational variability of parallel arrays of cortical microtubules under the outer cell wall of the helianthus hypocotyl epidermis

The epidermis of Helianthus hypocotyl can be peeled off and, in the form of detached strips can be used as a model system to study the effect on cortical microtubule (cMTs) orientation of these factors, which are difficult to be manipulated in situ, such as apoplastic pH or applied stress. In the first step, however, the orientation and reorientation of cMTs in the epidermis in situ must be described. The cMTs under the epidermal wall in hypocotyl epidermis at different positions along the hypocotyl and on its opposite sides were studied by means of immunostaining, using epi-fluorescence microscopy. The angle l that parallel array of cMTs makes with cell longitudinal axis was measured. The variation of l in a population of cells was documented by l-histogram (frequency of cells exhibiting a particular l±Dl plotted against l value). The histograms were of either transverse type (maximum at l ~90°, denoted as type A) or oblique type (two maxima on both sides of the transverse direction, denoted as type B) in the apical part of the hypocotyl, and were either of B type or of longitudinal type (maximum at l ~0° or 180° denoted as type C) in the basal part. The change from A or B to C basipetally may be considered as due to the developmental trend in cMT orientation. The occurrence of B above A in some hypocotyls in their apical part strengthens the hypothesis on the autonomous reorientation of cMTs. The intermingled occurrence of Aand B reorientation in the upper part of hypocotyl is interpreted as amanifestation of a subtle control of cell growth in latitudinal direction. The majority of histograms were asymmetric showing predominance of cMT parallel arrays inclined as the middle part of the letter Z

Shaping leaf vein pattern by auxin and mechanical feedback

This article comments on: Kneuper I, Teale W, Dawson JE, Tsugeki R, Katifori E, Palme K, Ditengou FA. 2021. Auxin biosynthesis and cellular efflux act together to regulate leaf vein patterning. Journal of Experimental Botany 72, 1151–1165. Auxin is an essential factor for the specification of veins in plant organs. The distribution of auxin in tissues depends on several physiological processes including auxin biosynthesis and transport. By using empirical data and theoretical analysis, Kneuper et al. (2021) explored a role for these processes in the establishment of leaf vasculature in Arabidopsis. They propose that the formation of early vein patterns may essentially be described in terms of auxin biosynthesis, its transport, and growth-dependent mechanical feedback from surrounding tissues

Semi-dwarfism and lodging tolerance in tef (Eragrostis tef) is linked to a mutation in the α-Tubulin 1 gene

The semi-dwarf and lodging-tolerant kegne mutant linked to defects in microtubule orientation has the potential to enhance the productivity of an African orphan crop tef (Eragrostis tef

Comparison of methods for obtaining doubled haploids of carrot

Doubled haploid lines of carrot can be obtained through androgenesis in anther cultures and in isolated microspore cultures. The two methods were compared using three carrot cultivars (‘Kazan F1’, ‘Feria F1’, and ‘Narbonne F1’) at the androgenesis induction stage, during plant regeneration from embryos, and during acclimatization of androgenetic plants as well as their characterization. It was found that cultivar was the main factor affecting the efficiency at each stage of plant production in both anther and isolated microspore cultures. The efficiency of androgenesis in anther cultures of ‘Feria F1’ was considerably higher in comparison with isolated microspore cultures, and more plants were obtained from the embryos of androgenesis-cultured plants. In ‘Kazan F1’ and ‘Narbonne F1’, more acclimatized androgenetic plants were produced from anther cultures. Ploidy assessment of acclimatized plants of ‘Narbonne F1’ showed that the majority of the plants in the population derived from anther cultures had a doubled chromosome (DH) set. On the other hand, the majority of plants obtained from isolated microspore cultures were haploids. When assessing homozygosity, it was found among plants obtained in anther cultures that the percentage of homozygotes for phosphoglucose isomerase (PGI) and aspartate aminotransferase (AAT) depended on the cultivar. In contrast, the majority of plants derived from isolated microspore cultures were homozygous regardless of cultivar

Mechanical control of morphogenesis at the shoot apex

Morphogenesis does not just require the correct expression of patterning genes; these genes must induce the precise mechanical changes necessary to produce a new form. Mechanical characterization of plant growth is not new; however, in recent years, new technologies and interdisciplinary collaborations have made it feasible in young tissues such as the shoot apex. Analysis of tissues where active growth and developmental patterning are taking place has revealed biologically significant variability in mechanical properties and has even suggested that mechanical changes in the tissue can feed back to direct morphogenesis. Here, an overview is given of the current understanding of the mechanical dynamics and its influence on cellular and developmental processes in the shoot apex. We are only starting to uncover the mechanical basis of morphogenesis, and many exciting questions remain to be answere

Chiral changes of cortical microtubule orientations in epidermls of sunflower hypocotyls. The effect of blue and red light

Light and developmental processes affect the cortical microtubule (cMT) orientation. The cMT orientation with a special regard to its chirality was analyzed under the outer epidermal cell walls in different regions of sunflower hypocotyls kept in darkness and after irradiation with blue and red light. The results show that the cMT orientation depends on the cell position along hypocotyl, but generally cMTs are oblique. The oblique orientation has defined chirality: either of Z-form (right-handed) or S-form (left-handed). In the lower region of hypocotyls the Z-form dominates. After irradiation of hypocotyls with blue light this domination has been maintained and appeared also in the upper region. In contrast, after irradiation with red light the Z-form domination has not been apparent. It is proposed that in darkness, variations of cMT orientations in the epidermis along the hypocotyl are due to developmental processes, while blue and red light affect the cMT orientation via "shifting" these processes backward and forward, respectively

Plant Biomechanics - A Natural Transition from Molecular to Organ Scale

"Plants are multicellular organisms of a unique structure because their tissues consist of two interwoven networks: a network of interconnected protoplasts that is embedded in a network of tightly joined cell walls. Such a structure has significant implications from both developmental and biomechanical perspectives. First, it facilitates mechanical signaling and integration at the organ level. Second, plant tissues can be regarded as cellular solids [1]. An emerging mechanical property of such “constructed” plant organs is that they are prestressed. In the case of green plant organs, built mainly of living tissues, the cellular solids are pressurized by turgid protoplasts. Because tissues within the organ differ in cell size and cell wall stiffness, this pressurization leads to different stresses in different organ portions. Woody stems of living trees are also prestressed. Although they are built mainly of dead cells, the prestress develops during their differentiation. Such natural prestressed constructions are analogous to prestressed concrete, which revolutionized architecture, e.g., the construction of bridges. Also, in the case of plant organs, the prestress, referred to as tissue stress or tensegrity at the organ scale, improves their mechanical performance [2,3]. However, another consequence of such a plant construction is that biomechanical processes acting at subcellular, cellular, and organ scales are closely related and hard to separate, while investigations of molecular mechanisms, in which mechanical factors are involved, are by rule blended with tissue and organ level research." [...] (fragm.