Stem Cell Basis for Fractal Patterns: Axillary Meristem Initiation

Whereas stem cell lineages are of enormous importance in animal development, their roles in plant development have only been appreciated in recent years. Several specialized lineages of stem cells have been identified in plants, such as meristemoid mother cells and vascular cambium, as well as those located in the apical meristems. The initiation of axillary meristems (AMs) has recently gained intensive attention. AMs derive from existing stem cell lineages that exit from SAMs and define new growth axes. AMs are in fact additional rounds of SAMs, and display the same expression patterns and functions as the embryonic SAM, creating a fractal branching pattern. Their formation takes place in leaf-meristem boundaries and mainly comprises two key stages. The first stage is the maintenance of the meristematic cell lineage in an undifferentiated state. The second stage is the activation, proliferation, and re-specification to form new stem cell niches in AMs, which become the new postembryonic “fountain of youth” for organogenesis. Both stages are tightly regulated by spatially and temporally interwound signaling networks. In this mini-review, I will summarize the most up-to-date understanding of AM establishment and mainly focus on how the leaf axil meristematic cell lineage is actively maintained and further activated to become CLV3-expressed stem cells, which involves phytohormonal cascades, transcriptional regulations, epigenetic modifications, as well as mechanical signals.

Cell division in the shoot apical meristem is a trigger for miR156 decline and vegetative phase transition in Arabidopsis

What determines the rate at which a multicellular organism matures is a fundamental question in biology. In plants, the decline of miR156 with age serves as an intrinsic, evolutionarily conserved timer for the juvenile-to-adult phase transition. However, the way in which age regulates miR156 abundance is poorly understood. Here, we show that the rate of decline in miR156 is correlated with developmental age rather than chronological age. Mechanistically, we found that cell division in the apical meristem is a trigger for miR156 decline. The transcriptional activity of MIR156 genes is gradually attenuated by the deposition of the repressive histone mark H3K27me3 along with cell division. Our findings thus provide a plausible explanation of why the maturation program of a multicellular organism is unidirectional and irreversible under normal growth conditions and suggest that cell quiescence is the fountain of youth in plants.

Schumpeter, Creative Destruction and the American Economy

The world is experiencing the age of Schumpeter and the American economy remains the premier example of a Schumpeterian economy. Despite its many naysayers and the doom and gloom professors that never stop predicting its demise, the American economy continues to show a remarkable capacity to rejuvenate. Orwell once commented that “England is perhaps the only great country whose intellectuals are ashamed of their nationality.” Left-wing intellectuals, he argued, hasted the divorce between intelligence and patriotism, which weakened the country’s morale and emboldened its enemies. Left-wing intellectuals, he argued, hasted the divorce between intelligence and patriotism, which weakened the country’s morale and emboldened its enemies. If he were alive today, it would be interesting to hear his opinion about the relentless barrage of criticism against everything American. One thing seems sure, though, America, not England, is the country most hated by its intellectual class. Any talk about Schumpeter’s “gale of creative destruction” is anathema to these “critical critics.” After all, when it comes to everything American, these individuals believe that they must criticize for the sake of criticism. The thought that capitalism has an internal mechanism akin to a fountain of youth must be disheartening to those whose blinders prevent them from accepting opposing facts. Frightenedly, these same intellectuals are apologists for every dictatorship the world over.

The leaf senescence-promoting transcription factor AtNAP activates its direct target gene CYTOKININ OXIDASE 3 to facilitate senescence processes by degrading cytokinins

Cytokinins (CKs) are a class of adenine-derived plant hormones that plays pervasive roles in plant growth and development including cell division, morphogenesis, lateral bud outgrowth, leaf expansion and senescence. CKs as a “fountain of youth” prolongs leaf longevity by inhibiting leaf senescence, and therefore must be catabolized for senescence to occur. AtNAP, a senescence-specific transcription factor has a key role in promoting leaf senescence. The role of AtNAP in regulating CK catabolism is unknown. Here we report the identification and characterization of AtNAP-AtCKX3 (cytokinin oxidase 3) module by which CKs are catabolized during leaf senescence in Arabidopsis. Like AtNAP, AtCKX3 is highly upregulated during leaf senescence. When AtNAP is chemically induced AtCKX3 is co-induced; and when AtNAP is knocked out, the expression of AtCKX3 is abolished. AtNAP physically binds to the cis element of the AtCKX3 promoter to direct its expression as revealed by yeast one-hybrid assays and in planta experiments. Leaves of the atckx3 knockout lines have higher CK concentrations and a delayed senescence phenotype compared with those of WT. In contrast, leaves with inducible expression of AtCKX3 have lower CK concentrations and exhibit a precocious senescence phenotype compared with WT. This research reveals that AtNAP transcription factor˗AtCKX3 module regulates leaf senescence by connecting two antagonist plant hormones abscisic acid and CKs.

Explaining the Quiddity of Prophet Khidr (PBUH) with the Focus on Interpretive Analysis of Verses 60 to 82 of Surah Al-Kahf and Removing Doubts About It

The story of the meeting of Prophet Moses with Prophet Khidr is mentioned in verses 60 to 82 of Surah al-Kahf. The latter is introduced as Khidr in the narrations and in the following years he also met with the Imams, on the basis of which his long life has been discussed. This story has many ambiguities and doubts. How the Prophet Moses, as the 'Ulu al-ʿAzm Prophet, followed that person and the deeds done by the wise person, which is not accepted in any divine law, and this has left much discussions for the commentators. The cause of this endless life is not well known. Most commentators have gone into the confusing details of the story and tried to resolve it. They have considered Moses' obedience to Khidr outside the legislative system and due to the evolution of Khidr's actions, they have considered a different personality for him that has no similar texts anywhere and attributed the long life of this personality to drinking the Fountain of Youth. These questionable justifications led to the study of the essence of the problem and the identification of the nature of Khidr’s personality from different angles. According to the interpretation of the Qur'an by the Qur'an, we have examined the various dimensions of the story in order to gain a Qur'anic knowledge of this character. At first glance, this story does not have the same in other verses, but in many similarities in the identity, duties and deeds of Khidr with the angels, the possibility has been stronger that Khidr has been an angel. Introducing Prophet Khidr not as a human being but as an angel including the divine messenger angels can answer all questions and doubts accurately and without any conflict and opposition with the Qur'an and religious principles and Shiism.

Nicotinamide Adenine Nucleotide—The Fountain of Youth to Prevent Oocyte Aging?

According to the U.S. Special Operations Command (SOCOM), new clinical trials of an anti-aging oral treatment using nicotinamide adenine nucleotide are planned for 2022. All over the globe, the discovery of the fountain of youth is still a great goal to reach, not only among aging researchers, since people desire to stay longer healthy and feel young when reaching old age. Since the 1960s, women delaying pregnancy to pursue higher educational levels and a career path has contributed to drastically diminished overall female fertility rates (e.g., number of born offspring/woman). Consequently, a growing number of advanced-aged women depend on assisted reproductive technologies (ART) to become pregnant. In 2019, the Society for Assisted Reproductive Technology reported 293672 cycles for oocyte retrieval. This change of demographics influenced women’s age of having their first child, which has increased significantly. However, their reproductive tract shows hallmarks of aging very early in life without an effective preventive treatment. Therefore, we will present whether NAD+ could help to prevent oocyte aging.

The nucleus pulposus microenvironment in the intervertebral disc: the fountain of youth?

The intervertebral disc (IVD) is a complex tissue, and its degeneration remains a problem for patients, without significant improvement in treatment strategies. This mostly age-related disease predominantly affects the nucleus pulposus (NP), the central region of the IVD. The NP tissue, and especially its microenvironment, exhibit changes that may be involved at the outset or affect the progression of IVD pathology. The NP tissue microenvironment is unique and can be defined by a variety of specific factors and components characteristic of its physiology and function. NP progenitor cell interactions with their surrounding microenvironment may be a key factor for the regulation of cellular metabolism, phenotype, and stemness. Recently, celltransplantation approaches have been investigated for the treatment of degenerative disc disease, highlighting the need to better understand if and how transplanted cells can give rise to healthy NP tissue. Hence, understanding all the components of the NP microenvironment seems to be critical to better gauge the success and outcomes of approaches for tissue engineering and future clinical applications. Knowledge about the components of the NP microenvironment, how NP progenitor cells interact with them, and how changes in their surroundings can alter their function is summarised. Recent discoveries in NP tissue engineering linked to the microenvironment are also reviewed, meaning how crosstalk within the microenvironment can be adjusted to promote NP regeneration. Associated clinical problems are also considered, connecting bench-to-bedside in the context of IVD degeneration.

Melatonin to Rescue the Aged Heart: Antiarrhythmic and Antioxidant Benefits

Aging comes with gradual loss of functions that increase the vulnerability to disease, senescence, and death. The mechanisms underlying these processes are linked to a prolonged imbalance between damage and repair. Damaging mechanisms include oxidative stress, mitochondrial dysfunction, chronodisruption, inflammation, and telomere attrition, as well as genetic and epigenetic alterations. Several endogenous tissue repairing mechanisms also decrease. These alterations associated with aging affect the entire organism. The most devastating manifestations involve the cardiovascular system and may lead to lethal cardiac arrhythmias. Together with structural remodeling, electrophysiological and intercellular communication alterations during aging predispose to arrhythmic events. Despite the knowledge on repairing mechanisms in the cardiovascular system, effective antiaging strategies able to reduce the risk of arrhythmias are still missing. Melatonin is a promising therapeutic candidate due to its pleiotropic actions. This indoleamine regulates chronobiology and endocrine physiology. Of relevance, melatonin is an antiaging, antioxidant, antiapoptotic, antiarrhythmic, immunomodulatory, and antiproliferative molecule. This review focuses on the protective effects of melatonin on age-induced cardiac functional and structural alterations, potentially becoming a new fountain of youth for the heart.