WUSCHEL-related homeobox family genes in rice control lateral root primordium size.

The development of a plastic root system is essential for stable crop production under variable environments. Rice plants have two types of lateral roots (LRs): S-type (short and thin) and L-type (long, thick, and capable of further branching). LR types are determined at the primordium stage, with a larger primordium size in L-types than S-types. Despite the importance of LR types for rice adaptability to variable water conditions, molecular mechanisms underlying the primordium size control of LRs are unknown. Here, we show that two WUSCHEL-related homeobox (WOX) genes have opposing roles in controlling LR primordium (LRP) size in rice. Root tip excision on seminal roots induced L-type LR formation with wider primordia formed from an early developmental stage. QHB/OsWOX5 was isolated as a causative gene of a mutant that is defective in S-type LR formation but produces more L-type LRs than wild-type (WT) plants following root tip excision. A transcriptome analysis revealed that OsWOX10 is highly up-regulated in L-type LRPs. OsWOX10 overexpression in LRPs increased the LR diameter in an expression-dependent manner. Conversely, the mutation in OsWOX10 decreased the L-type LR diameter under mild drought conditions. The qhb mutants had higher OsWOX10 expression than WT after root tip excision. A yeast one-hybrid assay revealed that the transcriptional repressive activity of QHB was lost in qhb mutants. An electrophoresis mobility shift assay revealed that OsWOX10 is a potential target of QHB. These data suggest that QHB represses LR diameter increase, repressing OsWOX10 Our findings could help improve root system plasticity under variable environments.

Coronary artery lumen complexity as a new marker for refractory symptoms in patients with vasospastic angina.

Refractory angina is an independent predictor of adverse events in patients with vasospastic angina (VSA). The aim of this study was to investigate the relationship between coronary lumen complexity and refractory symptoms in patients with VSA. Seventeen patients with VSA underwent optical coherence tomography. The patients were divided into the refractory VSA group (n = 9) and the stable VSA group (n = 8). A shoreline development index was used to assess the coronary artery lumen complexity. Shear stress was estimated using a computational fluid dynamics model. No difference was observed in the baseline characteristics between the two groups. The refractory VSA group showed the higher shoreline development index (refractory VSA 1.042 [1.017-1.188] vs stable VSA 1.003 [1.006-1.025], p = 0.036), and higher maximum medial thickness (refractory VSA 184 ± 17 µm vs stable VSA 148 ± 31 µm, p = 0.017), and higher maximum shear stress (refractory VSA 14.5 [12.1-18.8] Pa vs stable VSA 5.6 [3.0-10.5] Pa, p = 0.003). The shoreline development index positively correlates with shear stress (R2 = 0.46, P = 0.004). Increased medial thickness of the coronary arteries provokes lumen complexity and high shear stress, which might cause refractory symptoms in patients with VSA. The shoreline index could serve as a marker for irritability of the medial layer of coronary arteries and symptoms.

SLL1, which encodes a member of the stearoyl-acyl carrier protein fatty acid desaturase family, is involved in cell elongation in lateral roots via regulation of fatty acid content in rice.

We have identified a gene, SHORT LATERAL ROOT LENGTH1 (SLL1), which is important for the elongation of lateral roots in rice. An sll1 mutant has decreased lateral root growth due to a defect in the cell elongation. The SLL1 gene encodes a member of the stearoyl-acyl carrier protein fatty acid desaturase family that is the key regulator of overall fatty acid desaturation in plants. We measured the fatty acid content and found that the 18:0 content in the sll1 mutant root was approximately 4 times that in the wild-type root. When the sll1 mutant was grown at 33 °C, it complemented the mutant phenotype to a moderate level, which reflects the importance of the low 18:0 content in maintaining the cell membrane structure. The SLL1 gene was expressed at the lateral root tip, whereas SLL1 expression was not detected in the elongation zone of the crown roots. These results indicate that the lateral root specific defect in sll1 mutant is caused by the different expression patterns of SLL1 in lateral and crown roots. In addition, SLL1 over-expressers produced significantly longer lateral roots compared to the wild-type, and thus SLL1 gene would be very useful for improving rice root architecture.