Adventitious (crown) roots account for the majority of the root system of monocots. It is reported that auxin plays an important role in the formation of crown roots, but the underlying molecular mechanisms are still unknown. We characterized a rice (Oryza sativa L.) mutant crown rootless4 (crl4) that was found to have defective crown root formation. Besides reduced crown root number, the crl4 mutant showed auxin-related abnormal phenotypical characteristics such as reduced lateral root number and impaired root gravitropism. CRL4 encodes a protein highly homologous with Arabidopsis GNOM, which mediates auxin-dependent plant growth by coordinating the polar localization of auxin efflux carrier PIN1. In the crl4 mutant, auxin transport was impaired in shoots and roots. Besides, the GUS staining controlled by DR5 promoter in the node of crl4 mutant was fainter and spread wider than that of wild-type. These results indicate that maintaining an appropriate auxin accumulation and gradient through CRL4 in the basal portion of shoots is essential for crown root formation in rice.

Auxin flow is important for different root developmental processes such as root formation, emergence, elongation and gravitropism. However, the detailed information about the mechanisms regulating the auxin flow is less well understood in rice. We characterized the auxin transport-related mutants, Ospin-formed2-1 (Ospin2-1) and Ospin2-2, which exhibited curly root phenotypes and altered lateral root formation patterns in rice. The OsPIN2 gene encodes a member of the auxin efflux carrier proteins that possibly regulates the basipetal auxin flow from the root tip toward the root elongation zone. According to DR5-driven GUS expression, there is an asymmetric auxin distribution in the mutants that corresponded with the asymmetric cell elongation pattern in the mutant root tip. Auxin transport inhibitor, N-1-naphthylphthalamic acid and Ospin2-1 Osiaa13 double mutant rescued the curly root phenotype indicating that this phenotype results from a defect in proper auxin distribution. The typical curly root phenotype was not observed when Ospin2-1 was grown in distilled water as an alternative to tap water, although higher auxin levels were found at the root tip region of the mutant than that of the wild-type. Therefore, the lateral root formation zone in the mutant was shifted basipetally compared with the wild-type. These results reflect that an altered auxin flow in the root tip region is responsible for root elongation growth and lateral root formation patterns in rice.

Our findings indicate that the clinical courses of patients with deletions of both KCNQ2 and CHRNA4 are indistinguishable from those of patients with deletions of KCNQ2 only.

We report the activity of recombinant human surfactant apoprotein-C (rSP-C[Cys]2) and various phospholipids in a preterm rabbit model of respiratory distress syndrome (RDS). Mixtures of rSP-C(Cys)2 and certain phospholipids had similar activity (lung compliance and lung pressure-volume behavior) to rabbit surfactant in this model. The activity of rSP-C(Cys)2 was maximal at 1 mol% protein and varied significantly with the phospholipid composition. Chemically synthesized SP-C had similar activity to rSP-C(Cys)2. Deletion of six amino-terminal residues did not affect function. Substitution of cysteines and cysteine6 with adjacent serines (rSP-C[Ser]2) by site-specific mutagenesis minimized aggregation of rSP-C but did not affect activity. Palmitoylation of cysteine5 and cysteine6 in rSP-C (rSP-C[C16]2) did not enhance the activity of rSP-C(Cys)2. We conclude that bacterial expression is a practical source of functional SP-C, and that nonacylated forms of SP-C may be useful adjuvants to phospholipids in the treatment of RDS and possibly other forms of acute lung injury.

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