Phosphate starvation regulates cellulose synthesis to modify root growth.

In the model plant Arabidopsis (Arabidopsis thaliana), the absence of the essential macro-nutrient phosphate reduces primary root growth through decreased cell division and elongation, requiring alterations to the polysaccharide-rich cell wall surrounding the cells. Despite its importance, the regulation of cell wall synthesis in response to low phosphate levels is not well understood. In this study, we show that plants increase cellulose synthesis in roots under limiting phosphate conditions, which leads to changes in the thickness and structure of the cell wall. These changes contribute to the reduced growth of primary roots in low-phosphate conditions. Furthermore, we found that the cellulose synthase complex (CSC) activity at the plasma membrane increases during phosphate deficiency. Moreover, we show that this increase in the activity of the CSC is likely due to alterations in the phosphorylation status of cellulose synthases in low-phosphate conditions. Specifically, phosphorylation of CELLULOSE SYNTHASE 1 (CESA1) at the S688 site decreases in low-phosphate conditions. Phosphomimic versions of CESA1 with an S688E mutation showed significantly reduced cellulose induction and primary root length changes in low-phosphate conditions. Protein structure modeling suggests that the phosphorylation status of S688 in CESA1 could play a role in stabilizing and activating the CSC. This mechanistic understanding of root growth regulation under limiting phosphate conditions provides potential strategies for changing root responses to soil phosphate content.

The fnr-like mutants confer isoxaben tolerance by initiating mitochondrial retrograde signalling.

Isoxaben is a pre-emergent herbicide used to control broadleaf weeds. While the phytotoxic mechanism is not completely understood, isoxaben interferes with cellulose synthesis. Certain mutations in cellulose synthase complex proteins can confer isoxaben tolerance; however, these mutations can cause compromised cellulose synthesis and perturbed plant growth, rendering them unsuitable as herbicide tolerance traits. We conducted a genetic screen to identify new genes associated with isoxaben tolerance by screening a selection of Arabidopsis thaliana T-DNA mutants. We found that mutations in a FERREDOXIN-NADP(+) OXIDOREDUCTASE-LIKE (FNRL) gene enhanced tolerance to isoxaben, exhibited as a reduction in primary root stunting, reactive oxygen species accumulation and ectopic lignification. The fnrl mutant did not exhibit a reduction in cellulose levels following exposure to isoxaben, indicating that FNRL operates upstream of isoxaben-induced cellulose inhibition. In line with these results, transcriptomic analysis revealed a highly reduced response to isoxaben treatment in fnrl mutant roots. The fnrl mutants displayed constitutively induced mitochondrial retrograde signalling, and the observed isoxaben tolerance is partially dependent on the transcription factor ANAC017, a key regulator of mitochondrial retrograde signalling. Moreover, FNRL is highly conserved across all plant lineages, implying conservation of its function. Notably, fnrl mutants did not show a growth penalty in shoots, making FNRL a promising target for biotechnological applications in breeding isoxaben tolerance in crops.

Fetal Gas Gangrene: A Rare and Critical Case.

Gas gangrene is a lethal necrotic infection resulting in gas production within tissue. It is typically associated with trauma and is especially lethal during pregnancy, resulting in severe maternal infection and fetal death. We report the case of a 31-year-old G3P2 female who presented to the emergency department with abdominal bloating, vaginal cramping, and brown vaginal discharge. Physical examination showed that the patient was hypertensive, tachycardic, and tachypneic, and laboratory examination showed a downtrending beta-human chorionic gonadotropin and leukocytosis, with elevated inflammatory markers. Ultrasound showed copious gas located within the lower abdomen and the fetus was not visualized. Computed tomography (CT) of the abdomen and pelvis showed a gravid uterus with a single fetus and extensive air locules in the fetus, amniotic cavity, and placenta. The findings were consistent with gas gangrene of a mature fetus in the third trimester. Fetal gas gangrene is a potentially lethal condition during pregnancy, and early diagnosis is imperative in management. CT was utilized in this case to outline the increased gas production within the amniotic cavity and fetal organs and proved crucial in determining the next steps of management.