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R Amasino

Publications and source records attributed to R Amasino.

7 recordsLinked to original sources
PubMed2006

Effects of cytokinin production under two SAG promoters on senescence and development of tomato plants.

Two promoters of senescence-associated ARABIDOPSIS genes, SAG12 and SAG13, were used in tomato plants to express IPT that catalyzes the rate-limiting step in cytokinin biosynthesis. Expression of these heterologous promoters in tomato plants was analyzed using the reporter gene beta-glucuronidase. Both promoters are expressed in tomato leaves in a manner similar to their expression in ARABIDOPSIS plants. The SAG12 promoter is very specific to senescing leaves, whereas the SAG13 promoter is expressed in mature leaves prior to the onset of visible senescence and its expression increases in senescing leaves. Expression of both promoters in tomato tissues other than leaves was very low . IPT expressed under the control of SAG12 and SAG13 promoters ( PSAG12::IPT and PSAG13::IPT, respectively) resulted in suppression of leaf senescence and advanced flowering, as well as in a slight increase in fruit weight and fruit total soluble solids (TSS). However, expression of PSAG13::IPT also led to stem thickening, short internodal distances and loss of apical dominance. In contrast to the autoregulation of PSAG12::IPT, PSAG13::IPT is expressed at higher levels in mature leaves. This difference is likely due to PSAG13::IPT exhibiting two phases of expression - a senescence-independent expression prior to the onset of senescence that is not subjected to autoregulation by cytokinin, and enhanced expression throughout senescence which is autoregualted by cytokinin. This moderate different autoregulated behavior of PSAG12::IPT and PSAG13::IPT markedly influenced plant development, emphasizing the biological effects of cytokinin in addition to senescence inhibition.

Alcohol Oxidoreductases↗
PubMed2000

Molecular analysis of FRIGIDA, a major determinant of natural variation in Arabidopsis flowering time.

Vernalization, the acceleration of flowering by a long period of cold temperature, ensures that many plants overwinter vegetatively and flower in spring. In Arabidopsis, allelic variation at the FRIGIDA (FRI) locus is a major determinant of natural variation in flowering time. Dominant alleles of FRI confer late flowering, which is reversed to earliness by vernalization. We cloned FRI and analyzed the molecular basis of the allelic variation. Most of the early-flowering ecotypes analyzed carry FRI alleles containing one of two different deletions that disrupt the open reading frame. Loss-of-function mutations at FRI have thus provided the basis for the evolution of many early-flowering ecotypes.

Alleles↗
PubMed1993

Analysis of naturally occurring late flowering in Arabidopsis thaliana.

We have examined the late-flowering behavior of two ecotypes of Arabidopsis thaliana, Sf-2 and Le-0. The late-flowering trait segregates as a single dominant gene in crosses with the early-flowering Columbia ecotype. This gene, which we refer to as FLA, is located at one end of chromosome 4 between RFLP markers 506 and 3843 and is thus distinct from previously mapped genes that affect flowering time. The extreme delay in flowering time caused by the FLA gene can be overcome by vernalization in both the ecotypes in which it occurs naturally and in the Columbia ecotype into which this gene has been introgressed.

Arabidopsis↗
PubMedDate not supplied

Analysis of flowering time in ecotypes of Arabidopsis thaliana.

There exists variation in the timing of the initiation of flowering among different ecotypes of Arabidopsis thaliana. We have examined the basis of this variation between the early flowering Columbia (Col) ecotype and the late flowering ecotypes. Coimbra (Co-4), Geneva (Ge-2), and Zu-rich (Zu-0). In crosses of Col to Co-4, Ge-2, and Zu-0, the late flowering trait behaved as a single dominant gene the F1 plants were late flowering and in segregating F, populations a 3:1 ratio of late to early flowering plants was observed. This dominant gene resides in a region of chromosome 4 that contains a gene (FRIGIDA) conferring late flowering in certain other Arabidopsis ecotypes. Allelism tests indicate that the same genesis responsible for late flowering in Co-4, Ge-2. Zu-0, and the San Feliu (Sf-2) ecotype. These and previous results indicate that FRIGIDA accounts for much of the later flowering observed in various ecotypes of Arabidopsis.

Arabidopsis↗