Untitled

Abstract

The structure of the gene encoding the apoprotein of phytochrome B (PHYB1) in tomato has been determined from genomic and cDNA sequences. In contrast to PHYA, PHYB1 lacks an intron upstream of the first ATG. A single transcription start site was found by 5' RACE at -116. Tomato PHYB1 spans 7 kb starting from the first ATG. The coding region is organized into four exons as for other angiosperm PHY. The deduced apoprotein consists of 1131 amino acids, with a molecular mass of 125.4 kDa. Tomato phytochrome B1 shares 78% and 74% identity with Arabidopsis phytochromes B and D, respectively. Along with the normally spliced full-length transcripts, sequences of reverse transcriptase-PCR clones revealed five types of alternative transcripts. Each type of alternative transcript was missing a considerable part of the coding region, including the chromophore-binding site. The four putative PHYB1 mutants in tomato, which are temporarily red-light insensitive (tri), were each confirmed to have a mutation in PHYB1. Each mutation arose from a different, single-base substitution. Allele tri1 is presumably a null because the mutation introduces a stop at codon 92. In tri3, val-238 is replaced by Phe. The importance of this valine residue is evidenced by the fact that the tri3 phenotype is as strong as that of tri1. Alleles tri2 and tri4 encode proteins truncated at their C-termini. The former lacks either 170 or 438 amino acids, depending upon which of two types of splicing occurs during transcript maturation, while the latter lacks 225.

Ectopic Expression Reveals a Conserved PHYB Homolog in Soybean

“…This revealed that the genomic sequence includes four exons (Figure 1B), as also is the case for the PHYB genes present in A. thaliana , potato [19], tomato[20], rice [11], [21] and maize [22] PHYB s. Although the exon lengths in GmPHYB1 were comparable with those in AtPHYB , the soybean introns were considerably larger (Figure 1B). …”

PHYTOCHROME‐INTERACTING FACTOR 3 mediates light‐dependent induction of tocopherol biosynthesis during tomato fruit ripening

“…The hp2 mutant is deficient for DET1 transcription factor, a negative regulator of light signal transduction (Soressi, 1975). phya, phyb1, phyb2, phyab1, phyb1b2, and phyab1b2 are loss-of-function mutants initially characterized by Kerckhoffs et al (1996); Kerckhoffs, Schreuder, Van Tuinen, Koornneef, and Kendrick (1997); Kerckhoffs et al (1999); Lazarova, Kerckhoffs, et al (1998); Lazarova, Kubota, et al (1998);and Weller, Schreuder, Smith, Koornneef, and Kendrick (2000).…”

Tomato phyE Is Required for Shade Avoidance in the Absence of phyB1 and phyB2

“…The PHYE amiRNA line, previously characterized phyB1 (Lazarova G. I. et al, 1998a ) and phyB2 (Weller et al, 2000 ) null mutants, and wild-type Moneymaker were characterized for the internode elongation shade avoidance response over time under long day high R:FR and low R:FR to induce the shade avoidance response in a growth chamber. Like phyB2 mutants, PHYE amiRNA plants have wild-type internode lengths in both high R:FR and low R:FR (Figure 4 ).…”

“…Interestingly, this work and that of others (Weller et al, 2000 ) shows a different role for the tomato phytochrome family members as compared to Arabidopsis. In order to investigate the role of the tomato PHYB family members, we took advantage of the previously characterized phyA (Lazarova G. I. et al, 1998b ), phyB1 (Lazarova G. I. et al, 1998a ), and phyB2 (Weller et al, 2000 ) null mutants and generated an artificial microRNA (amiRNA; Alvarez et al, 2006 ; Schwab et al, 2006 ; Warthmann et al, 2008 ) to knock down expression of PHYE mRNA ( PHYE amiRNA). In this manuscript, we characterize the role of phyE in both internode elongation and shade avoidance and demonstrate that phyE is required for shade avoidance in the absence of phyB1 and phyB2.…”