Improvement in nitrogen use efficiency: physiological and molecular approacheses

Nitrogen deficiency in agricultural systems is a world-wide problem. It is true of the Indian scenario as well. The utilization efficiency of nitrogenous fertilizers under field conditions is poor. This results in loss of a costly input and accentuates the environmental degradation. In this paper, the present status of our knowledge on physiological and molecular approaches to improve nitrogen utilization efficiency at the level of its uptake, assimilation and relationship to photosynthesis, a major factor determining biomass and grain yield, is discussed. The work done in the authors' laboratory for over a decade is summarized. It is hoped that better understanding will help to apply the tools of molecular biology to genetically manipulate the crop plants so as to enhance yields at low inputs of nitrogen

Somatic mutation and gain of copy number of PIK3CA in human breast cancer

INTRODUCTION: Phosphatidylinositol 3-kinases (PI3Ks) are a group of lipid kinases that regulate signaling pathways involved in cell proliferation, adhesion, survival, and motility. Even though PIK3CA amplification and somatic mutation have been reported previously in various kinds of human cancers, the genetic change in PIK3CA in human breast cancer has not been clearly identified. METHODS: Fifteen breast cancer cell lines and 92 primary breast tumors (33 with matched normal tissue) were used to check somatic mutation and gene copy number of PIK3CA. For the somatic mutation study, we specifically checked exons 1, 9, and 20, which have been reported to be hot spots in colon cancer. For the analysis of the gene copy number, we used quantitative real-time PCR and fluorescence in situ hybridization. We also treated several breast cancer cells with the PIK3CA inhibitor LY294002 and compared the apoptosis status in cells with and without PIK3CA mutation. RESULTS: We identified a 20.6% (19 of 92) and 33.3% (5 of 15) PIK3CA somatic mutation frequency in primary breast tumors and cell lines, respectively. We also found that 8.7% (8 of 92) of the tumors harbored a gain of PIK3CA gene copy number. Only four cases in this study contained both an increase in the gene copy number and a somatic mutation. In addition, mutation of PIK3CA correlated with the status of Akt phosphorylation in some breast cancer cells and inhibition of PIK3CA-induced increased apoptosis in breast cancer cells with PIK3CA mutation. CONCLUSION: Somatic mutation rather than a gain of gene copy number of PIK3CA is the frequent genetic alteration that contributes to human breast cancer progression. The frequent and clustered mutations within PIK3CA make it an attractive molecular marker for early detection and a promising therapeutic target in breast cancer

Nutritional potential of Vigna minima (Roxb.) Ohwi and Ohashi: I. Seed protein content and amino acid composition

The seed protein content and amino acid composition of 14 natural populations and their three-generation progenies (grown in different locations) belonging to Vigna minima (Roxb.) Ohwi & Ohashi and of V. umbellata cv IC 1568 have been investigated. The populations of V. minima were sampled from different ecozones of Western Ghats of Kerala and Tamil Nadu (India). The range of variation in protein levels is narrow, but the protein content of the coastal population is higher than the rice bean suggesting its breeding potential for high protein and salt tolerant lines of rice bean. Although the seed protein content shows genotype × environment interaction, there is a substantial genetic variability among the populations. The tenuous relationship between protein content and yield conponents suggest the presence of correlation breakers which can be utilized in breeding programmes of rice bean. There is a broad genetic base in the levels of essential amino acids, and the range of variation observed is higher than that recorded for different species of Vigna and Phaseolus. The wild relative is nutritionally as good as or superior to the cultigen