The Miniature1 Seed Locus of Maize Encodes a Cell Wall Invertase Required for Normal Development of Endosperm and Maternal Cells in the Pedicel.

Abstract

Collective evldence demonstrates that the MInlaturel (Mnl) seed locus in maize encodes an endosperm-specific lsozyme of cell wall Invertase, CWI-2. l h e evidence includes (1) isolatlon and characterizatlon of ethyl methanesulfonate-lnduced mnl mutants wlth altered enzyme actlvlty and (2) a near-linear relatlonshlp between geneldose and Invertase actlvlty and the CWI-2 proteln. In addltlon, molecular analyses showed that the cDNA clone Incw2 maps to the Mnl locus and dlfferentlates the slx ethyl methanesulfonate-lnduced mnl mutants of lndependent orlgin lnto two classes when RNA gel blot analyses were used. We also report two unexpected observatlons that provide slgnlflcant new lnslght lnto the physlologlcal role of Invertase and Its mgulatlon ln a developlng seed. First, a l a g e proportlon of total enzyme actlvlty (&90%) was dlspensable &e., nonllmltlng). However, below the threshold leve1 of -6% of wlld-type activlty, the endosperm enzyme controlled both the slnk strength of the developing endosperm as well as the developmental stablllty of maternal cells ln the pedicel ln a rate-limltlng manner. Our data also suggest an unusually tlght coordinate control between the cell wall-bound and the soluble forms of invertase, which are most likely encoded by two separate genes, presumably through metabolic controls mediated by the sugam

Aspergillus flavus infection induces transcriptional and physical changes in developing maize kernels

“…Three maize invertases (GRMZM2G139300, GRMZM2G394450, GRMZM2G123633) were more highly expressed in the A. flavus infected kernels than in non-infected kernels (Table 2; Figure 2). Invertases are responsible for hydrolyzing sucrose into glucose and fructose (Cheng et al, 1996; Chourey et al, 2006), and are important in maize kernel development (Weber et al, 1997; Roitsch et al, 2003). Up regulation of invertases in the maize kernel is predicted to cause an increase in free hexose levels in the kernel and affect seed storage reserves such as starch.…”

Targeting the AtCWIN1 Gene to Explore the Role of Invertases in Sucrose Transport in Roots and during Botrytis cinerea Infection

“…Altered CWIN activity severely impacts reproductive organs that are often symplasticaly isolated from the surrounding environment. For example, mutations in ZmCWIN2, OsCWIN2 ( OsGIF1 ), and SlCWIN1 ( Lin5 ) lead to the production of miniature seeds, a decrease in grain yield and an altered flower and fruit morphology, respectively (Cheng et al, 1996; Wang et al, 2008; Zanor et al, 2009). In Arabidopsis, atcwin4 mutant flowers did not produce nectar but accumulated more starch and less soluble sugars (Ruhlmann et al, 2010).…”

Linking Expression of Fructan Active Enzymes, Cell Wall Invertases and Sucrose Transporters with Fructan Profiles in Growing Taproot of Chicory (Cichorium intybus): Impact of Hormonal and Environmental Cues

“…Invertases comprise the evolutionarily related vacuolar (VI) and CWI, both existing in several isoforms, and a distinct group of cytosolic invertases (CI) (Sturm and Tang, 1999). High CWI activity creates a sucrose concentration gradient between the SE/CC complex and the surrounding cell wall matrix, thereby promoting phloem unloading and acting as an important regulator for carbon partitioning at whole plant level as demonstrated in mutant (Cheng et al, 1996; Wang et al, 2008) and transgenic studies (Zanor et al, 2009; Ruan et al, 2010). …”