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Glucosylceramides (GlcCer), glucose-conjugated sphingolipids, are major components of the endomembrane system and plasma membrane in most eukaryotic cells. Yet the quantitative significance and cellular functions of GlcCer are not well characterized in plants and other multi-organ eukaryotes. To address this, we examined Arabidopsis lines that were lacking or deficient in GlcCer by insertional disruption or by RNA interference ( RNAi) suppression of the single gene for GlcCer synthase ( GCS, At2g19880), the enzyme that catalyzes GlcCer synthesis. Null mutants for GCS (designated ' gcs-1') were viable as seedlings, albeit strongly reduced in size, and failed to develop beyond the seedling stage. Heterozygous plants harboring the insertion allele exhibited reduced transmission through the male gametophyte. Undifferentiated calli generated from gcs-1 seedlings and lacking GlcCer proliferated in a manner similar to calli from wild-type plants. However, gcs-1 calli, in contrast to wild-type calli, were unable to develop organs on differentiation media. Consistent with a role for GlcCer in organ-specific cell differentiation, calli from gcs-1 mutants formed roots and leaves on media supplemented with the glucosylated sphingosine glucopsychosine, which was readily converted to GlcCer independent of GCS. Underlying these phenotypes, gcs-1 cells had altered Golgi morphology and fewer cisternae per Golgi apparatus relative to wild-type cells, indicative of protein trafficking defects. Despite seedling lethality in the null mutant, GCS RNAi suppression lines with ≤2% of wild-type GlcCer levels were viable and fertile. Collectively, these results indicate that GlcCer are essential for cell-type differentiation and organogenesis, and plant cells produce amounts of GlcCer in excess of that required for normal development. [ABSTRACT FROM AUTHOR]

ABSTRACT "What's right with unemployment insurance" by far outweighs "What's wrong." There are, nevertheless, many flaws in the program--in philosophy, in benefits, in taxes, in administration. Most important is the need for consensus concerning primary goals. There is still no generally-accepted philosophy concerning the proper place and purpose of unemployment insurance in our economic system. Many workers currently exempt from coverage should be protected. Qualifying requirements for benefit eligibility, as well as disqualifying provisions, should be reexamined. Minimum and maximum weekly benefit amounts and potential duration provisions indicate inherent philosophies which are inconsistent and inequitable, which yield more generous benefits to unemployed secondary workers than to unemployed heads of families. Changes should relate qualifying employment and earnings, by sex, to minimum and maximum benefits and duration, in fixed proportions rather than in fixed amounts. Payroll tax bases vary considerably. Their impact among different industries is widely divergent. A supplemental flat-rate employee tax should help finance more adequate benefits. Pending agreement on primary goals, no practical solution to federal-state administrative problems can be suggested. Thereafter, however, authority and responsibility and costs should be fairly and dearly allocated between the federal government and the states. This would contribute to a much better partnership, program, and public image. [ABSTRACT FROM AUTHOR]