Differential Requirement for the Cell Wall Integrity Sensor Wsc1p in Diploids Versus Haploids

The primary role of the Cell Wall Integrity Pathway (CWI) in Saccharomyces cerevisiae is monitoring the state of the cell wall in response to general life cycle stresses (growth and mating) and imposed stresses (temperature changes and chemicals). Of the five mechanosensor proteins monitoring cell wall stress, Wsc1p and Mid2p are the most important. We find that WSC1 has a stringent requirement in zygotes and diploids, unlike haploids, and differing from MID2’s role in shmoos. Diploids lacking WSC1 die frequently, independent of mating type. Death is due to loss of cell wall and plasma membrane integrity, which is suppressed by osmotic support. Overexpression of several CWI pathway components suppress wsc1∆ zygotic death, including WSC2, WSC3, and BEM2, as well as the Rho-GAPS, BEM3 and RGD2. Microscopic observations and suppression by BEM2 and BEM3 suggest that wsc1∆ zygotes die during bud emergence. Downstream in the CWI pathway, overexpression of a hyperactive protein kinase C (Pkc1p-R398P) causes growth arrest, and blocks the pheromone response. With moderate levels of Pkc1p-R398P, cells form zygotes and the wsc1∆ defect is suppressed. This work highlights functional differences in the requirement for Wsc1p in diploids Versus haploids and between Mid2p and Wsc1p during mating.

Septin Assembly and Remodeling at the Cell Division Site During the Cell Cycle

The septin family of proteins can assemble into filaments that further organize into different higher order structures to perform a variety of different functions in different cell types and organisms. In the budding yeast Saccharomyces cerevisiae, the septins localize to the presumptive bud site as a cortical ring prior to bud emergence, expand into an hourglass at the bud neck (cell division site) during bud growth, and finally “split” into a double ring sandwiching the cell division machinery during cytokinesis. While much work has been done to understand the functions and molecular makeups of these structures, the mechanisms underlying the transitions from one structure to another have largely remained elusive. Recent studies involving advanced imaging and in vitro reconstitution have begun to reveal the vast complexity involved in the regulation of these structural transitions, which defines the focus of discussion in this mini-review.

A preferred sequence for organelle inheritance during polarized cell growth

Some organelles cannot be synthesized anew, so they are segregated into daughter cells during cell division. In Saccharomyces cerevisiae, daughter cells bud from mother cells and are populated by organelles inherited from the mothers. To determine whether this organelle inheritance occurs in a stereotyped manner, we tracked organelles using fluorescence microscopy. We describe a program for organelle inheritance in budding yeast. The cortical endoplasmic reticulum (ER) and peroxisomes are inherited concomitant with bud emergence. Next, vacuoles are inherited in small buds, followed closely by mitochondria. Finally, the nucleus and perinuclear ER are inherited when buds have nearly reached their maximal size. Because organelle inheritance timing correlates with bud morphology, which is coupled to the cell cycle, we tested whether disrupting the cell cycle alters organelle inheritance order. By arresting cell cycle progression but allowing continued bud growth, we determined that organelle inheritance still occurs when DNA replication is blocked, and that the general inheritance order is maintained. Thus, organelle inheritance follows a preferred order during polarized cell division and does not require completion of S-phase.

Reproductive biology of Vatica venulosa Blume (Dipterocarpaceae)

Widjaya AH, Latifah D, Hardwick KA, Suhartanto MR, Palupi ER. 2021. Reproductive biology of Vatica venulosa Blume (Dipterocarpaceae). Biodiversitas 22: 4327-4337. Vatica venulosa Blume is categorized as Critically Endangered A1c ver 2.3, according to the IUCN Red List. A study of the reproductive biology of V. venulosa Blume was carried out in August 2019-February 2020 at the Research Center for Plant Conservation and Botanic Gardens, Bogor, Indonesia. The research observed flower morphology, flower development, type of pollination, fruit and seed structures. V. venulosa is categorized as having a sub-annual flowering pattern. The flowering phenology of V. venulosa from flower bud emergence until fruit senescence takes about 6 months. The flower is hermaphroditic, with position of the pistil is higher/longer than the stamen; and pollen was released prior to stigma being receptive (protandrous). V. venulosa is a cross-pollinated plant, the flower visitors are insect nymphs of Thrips sp. (Thysanoptera: Thripidae), which are white and 1-1.5 mm in size. The percentage of blooming flowers was 32.3-37.9%, fruit set 10.9 %-12.6%. Seed physiological maturity is reached at the age of 101±3-106±3 days after the flowers bloom when the wings are yellow green or green orange in color. V. venulosa seed is a non endospermous seed, and the cotyledons are composed mainly of small clumps of starch, being 42.5% carbohydrate.

The budding yeast protein Chl1p is required for delaying progression through G1/S phase after DNA damage

Background The budding yeast protein Chl1p is a nuclear protein required for sister-chromatid cohesion, transcriptional silencing, rDNA recombination, ageing and plays an instrumental role in chromatin remodeling. This helicase is known to preserve genome integrity and spindle length in S-phase. Here we show additional roles of Chl1p at G1/S phase of the cell cycle following DNA damage. Results G1 arrested cells when exposed to DNA damage are more sensitive and show bud emergence with faster kinetics in chl1 mutants compared to wild-type cells. Also, more damage to DNA is observed in chl1 cells. The viability falls synergistically in rad24chl1 cells. The regulation of Chl1p on budding kinetics in G1 phase falls in line with Rad9p/Chk1p and shows a synergistic effect with Rad24p/Rad53p. rad9chl1 and chk1chl1 shows similar bud emergence as the single mutants chl1, rad9 and chk1. Whereas rad24chl1 and rad53chl1 shows faster bud emergence compared to the single mutants rad24, rad53 and chl1. In presence of MMS induced damage, synergistic with Rad24p indicates Chl1p’s role as a checkpoint at G1/S acting parallel to damage checkpoint pathway. The faster movement of DNA content through G1/S phase and difference in phosphorylation profile of Rad53p in wild type and chl1 cells confirms the checkpoint defect in chl1 mutant cells. Further, we have also confirmed that the checkpoint defect functions in parallel to the damage checkpoint pathway of Rad24p. Conclusion Chl1p shows Rad53p independent bud emergence and Rad53p dependent checkpoint activity in presence of damage. This confirms its requirement in two different pathways to maintain the G1/S arrest when cells are exposed to damaging agents. The bud emergence kinetics and DNA segregation were similar to wild type when given the same damage in nocodazole treated chl1 cells which establishes the absence of any role of Chl1p at the G2/M phase. The novelty of this paper lies in revealing the versatile role of Chl1p in checkpoints as well as repair towards regulating G1/S transition. Chl1p thus regulates the G1/S phase by affecting the G1 replication checkpoint pathway and shows an additive effect with Rad24p for Rad53p activation when damaging agents perturb the DNA. Apart from checkpoint activation, it also regulates the budding kinetics as a repair gene.

An organelle inheritance pathway during polarized cell growth

Some organelles cannot be synthesized anew, so they are segregated into daughter cells during cell division. In Saccharomyces cerevisiae, daughter cells bud from mother cells and are populated by organelles inherited from the mothers. To determine whether this organelle inheritance occurs in a stereotyped manner, we tracked organelles using fluorescence microscopy. We describe a program for organelle inheritance in budding yeast. The cortical endoplasmic reticulum (ER) and peroxisomes are inherited concomitant with bud emergence. Next, vacuoles are inherited in small buds, followed closely by mitochondria. Finally, the nucleus and perinuclear ER are inherited when buds have nearly reached their maximal size. Because organelle inheritance timing correlates with bud morphology, which is coupled to the cell cycle, we tested whether organelle inheritance order is controlled by the cell cycle. By arresting cell cycle progression but allowing continued bud growth, we determined that organelle inheritance still occurs without cell cycle progression past S-phase, and that the general inheritance order is maintained. Thus, organelle inheritance follows a preferred order during polarized cell division, but it is not controlled exclusively by cell cycle signaling.Summary statementOrganelles are interconnected by contact sites, but they must be inherited from mother cells into buds during budding yeast mitosis. We report that this process occurs in a preferred sequence.

Haspin Modulates the G2/M Transition Delay in Response to Polarization Failures in Budding Yeast

Symmetry breaking by cellular polarization is an exquisite requirement for the cell-cycle of Saccharomyces cerevisiae cells, as it allows bud emergence and growth. This process is based on the formation of polarity clusters at the incipient bud site, first, and the bud tip later in the cell-cycle, that overall promote bud emission and growth. Given the extreme relevance of this process, a surveillance mechanism, known as the morphogenesis checkpoint, has evolved to coordinate the formation of the bud and cell cycle progression, delaying mitosis in the presence of morphogenetic problems. The atypical protein kinase haspin is responsible for histone H3-T3 phosphorylation and, in yeast, for resolution of polarity clusters in mitosis. Here, we report a novel role for haspin in the regulation of the morphogenesis checkpoint in response to polarity insults. Particularly, we show that cells lacking the haspin ortholog Alk1 fail to achieve sustained checkpoint activation and enter mitosis even in the absence of a bud. In alk1Δ cells, we report a reduced phosphorylation of Cdc28-Y19, which stems from a premature activation of the Mih1 phosphatase. Overall, the data presented in this work define yeast haspin as a novel regulator of the morphogenesis checkpoint in Saccharomyces cerevisiae, where it monitors polarity establishment and it couples bud emergence to the G2/M cell cycle transition.

The budding yeast protein Chl1p is required for delaying progression through G1/S phase after DNA damage.

Background: The helicase Chl1p is a nuclear protein required for sister-chromatid cohesion, transcriptional silencing, rDNA recombination, ageing and plays an instrumental role in chromatin remodeling. This budding yeast protein is known to preserve genome integrity and spindle length in S-phase. Here we show additional roles of Chl1p at G1/S phase of the cell cycle following DNA damage. Results: G1 arrested cells when exposed to DNA damage are more sensitive and show bud emergence with a faster kinetics in chl1 mutants compared to wild-type cells. This role of Chl1p in G1 phase is Rad9p dependent and independent of Rad24 and Rad53. rad9chl1 shows similar bud emergence as the single mutants chl1 and rad9 whereas rad24chl1 and rad53chl1 shows faster bud emergence compared to the single mutants rad24 , rad53 and chl1 . In case of damage induced by genotoxic agent like hydroxyurea, Chl1p acts as a checkpoint at G1/S. The faster movement of DNA content through G1/S phase and difference in phosphorylation profile of Rad53p in wild type and chl1 cells confirms the checkpoint defect in chl1 mutant cells. Further we have observed that the checkpoint defect is synergistic with the replication checkpoint Sgs1p and functions in prallel to the checkpoint pathway of Rad24p. Conclusion: Chl1p shows Rad53p independent bud emergence and Rad53p dependent checkpoint, confirms its requirement in two different pathways to maintain the G1/S arrest when cells are exposed to damaging agents. The bud emergence kinetics and DNA segregation were similar to wild type when given the same damage in nocodazole treated chl1 cells which establishes the absence of any role of Chl1p at the G2/M phase. The novelty of this paper lies in revealing the versatile role of Chl1p in checkpoints as well as repair towards regulating G1/S transition. Chl1 thus regulates the G1/S phase by affecting the G1 replication checkpoint pathway and shows an additive effect with Rad24p as well as Rad53p activation when damaging agents perturbs the DNA.

Effects of organic manures and bio-fertilizers on growth, flowering and yield of China aster (Callistephus chinensis L. Nees var. Kamini)

Effects of organic manures and bio-fertilizers on growth, flowering and yield of China aster (Callistephus chinensis) var. kamini was investigated. The experiment with 12 treatment combinations comprising of FYM, vermicompost and bio-fertilizers viz., phosphate solublising bacteria (PSB) and Azospirillum was conducted. All the treatment combinations showed significant response in vegetative, flowering and yield characters during the entire investigation. The treatment combinations of Azospirillum + PSB + vermicompost + 50% RDF was found to be promising for maximum plant height (63.97 cm), plant spread (21.50 cm), stem girth (15.47 mm), number of primary branches per plants (12.33), number of secondary branches per plants (22.14), enhanced flower bud emergence (73.33 days), stalk length (32.20 cm), number of flowers per plant (24.35), flower diameter (46.18 mm), prolonged flower duration (23.05 days), flower yield (18.87 q/ha) and seed yield (2.44 q/ha) were on par with Azospirillum + PSB + FYM + 50% RDF.

Inflorescence morphology and development of suweg (Amorphophallus paeoniifolius (Dennst.) Nicolson

Hanfayani T, Yuzammi, Hadiah JT. 2020. Inflorescence morphology and development of suweg (Amorphophallus paeoniifolius (Dennst.) Nicolson. Biodiversitas 21: 5835-5844. Inflorescence of Amorphophallus paeoniifolius (Dennst.) Nicolson consists of two main parts: spathe and spadix. Detailed information on its development, however, is not yet available. This study aimed to investigate the development and morphology of suweg’s inflorescence, to reveal the anthesis of male and female flowers, and to observe its insect visitors. The study observed 46 inflorescences, ten of which were measured for detailed developments. Inflorescences were observed from bud emergence to withering during one flowering cycle. The results showed that the flowering process included six phases which altogether required 22 to 36 days, namely the developments of inflorescence bud, cataphyll, spathe and spadix, appendix, fully bloomed inflorescence, and flowers anthesis. The inflorescence height including peduncle was 48–75 cm, spathe 19–50 cm long, spathe circle 65–176 cm, appendix 13–33 cm long, and appendix circle 45–80 cm. Three appendix forms were observed: ovate (43.48%), triangular conic (41.30%), and rounded (15.22%). Female flower anthesis occurred one day prior to male flower anthesis. Insect visitors found during anthesis were Lucilia sericata (Calliphoridae), Sarcophaga sp. (Sarcophagidae), and Trigona speciosa (Apidae).