Artificial selection of the Green Revolution gene Semidwarf 1 is implicated in upland rice breeding

Semidwarf breeding has boosted crop production and is a well-known outcome from the first Green Revolution. The Green Revolution gene Semidwarf 1(SD1), which modulates gibberellic acid(GA) biosynthesis, plays a principal role in determining rice plant height. Mutations in SD1 reduce rice plant height and promote lodging resistance and fertilizer tolerance to increase grain production. The plant height mediated by SD1 also favors grain yield under certain conditions. However, it is not yet known whether the function of SD1 in upland rice promotes adaptation and grain production. In this study, the plant height and grain yield of irrigated and upland rice were comparatively analyzed under paddy and dryland conditions. In response to dryland environments, rice requires a reduction in plant height to cope with water deficits. Upland rice accessions had greater plant heights than their irrigated counterparts under both paddy and dryland conditions, and appropriately reducing plant height could improve adaptability to dryland environments and maintain high grain yield formation. Moreover, upland rice cultivars with thicker stem diameters had stronger lodging resistance, which addresses the lodging problem. Knockout of SD1 in the upland rice cultivar IRAT104 reduced the plant height and grain yield, demonstrating that the adjustment of plant height mediated by SD1 could increase grain production in dryland fields. In addition, an SD1 genetic diversity analysis verified that haplotype variation causes phenotypic variation in plant height. During the breeding history of rice, SD1 allelic mutations were selected from landraces to improve the grain yield of irrigated rice cultivars, and this selection was accompanied by a reduction in plant height. Thus, five known mutant alleles were analyzed to verify that functional SD1 is required for upland rice production. All these results suggest that SD1 might have undergone artificial positive selection in upland rice, which provides further insights concerning greater plant height in upland rice breeding.

PRELIMINARY STUDY ON SKIN CANCER DETECTION IN SENCAR MICE USING MUELLER OPTICAL COHERENCE TOMOGRAPHY

We report on the use of a fiber-based Mueller-matrix optical coherence tomography(OCT)system with continuous source-polarization modulation for in vivo imaging of early stages of skin cancer in SENCAR mice.A homemade hand-held probe with integrated optical scanning and beam delivering optics was coupled in the sample arm.The OCT images show the morphological changes in skin resulting from pre-cancerous papilloma formations that are consistent with histology,thus demonstrating the system’s potential for early skin cancer detection.

QUANTITATIVE EVALUATION OF RETINAL TUMOR VOLUME IN MOUSE MODEL OF RETINOBLASTOMA BY USING ULTRA HIGH-RESOLUTION OPTICAL COHERENCE TOMOGRAPHY

An ultra high resolution spectral-domain optical coherence tomography(SD-OCT)together with an advanced animal restraint and positioning system was built for noninvasive non-contact in vivo three-dimensional imaging of rodent models of ocular diseases.The animal positioning system allowed the operator to rapidly locate and switch the areas of interest on the retina.This function together with the capability of precise spatial registration provided by the generated OCT fundus image allows the system to locate and compare the same lesion(retinal tumor in the current study)at different time point throughout the entire course of the disease progression.An algorithm for fully automatic segmentation of the tumor boundaries and calculation of tumor volume was developed.The system and algorithm were successfully applied to monitoring retinal tumor growth quantitatively over time in the LHBETATAG mouse model of retinoblastoma.